Ukraine´s Prosecutor General said on Friday that his office would review the case of an energy company linked to Hunter Biden – just a day after President Donald Trump called for the country to investigate the Bidens.

The prosecutor said he is reviewing all the cases that were closed by his predecessors – including several related to the owner of gas company Burisma Holdings where former Vice President Joe Biden´s son sat on the board of directors and was reportedly compensated $50,000 a month.

The developments in Ukraine come after newly-revealed Ukraine texts show Trump administration officials discussing efforts to get a probe and push a set of talking points – including by leveraging a presidential visit.

President Trump, speaking on the South Lawn of the White House Thursday, said Ukraine should investigate the Bidens, while also saying China should probe Hunter Biden's business dealings there.

The president suggested on that China showered $1.5 billion on Hunter Biden in order to influence his father and win favorable trade deals with the United States.

House Democrats are conducting an impeachment inquiry of the president after a whistle-blower complaint detailed the president's July phone call to the president Ukraine where he pushed for a probe of his Democratic rival.

Trump defended his public call for foreign help investigating his rival a day after his initial comments in response to a question by DailyMail.com. His response fueled the uproar over his earlier Ukraine request, which helped jump-start a Democratic impeachment inquiry.

President Donald Trump said Thursday that both Ukraine and China should probe possible corruption by former Vice President Joe Biden and his son Hunter Biden

'As President I have an obligation to end CORRUPTION, even if that means requesting the help of a foreign country or countries. It is done all the time. This has NOTHING to do with politics or a political campaign against the Bidens. This does have to do with their corruption!' Trump tweeted Friday.

Trump said Thursday that if Ukraine 'were honest about it,' it 'would start a major investigation against the Bidens. It's a very simple answer.'

'Likewise, China should start an investigation into the Bidens,' Trump insisted, 'because what happened with the Bidens in China is just about as bad.

'President Zelensky – if it were me I would recommend they start an investigation into the Bidens because nobody has any doubt that they aren't crooked,' he added, speaking of the president of Ukraine.

Ukraine's Prosecutor General Ruslan Ryaboshapka said he would reopen a number of cases, including one dealing with the company where Hunter Biden served on the board

Ukrainian President Volodymyr Zelenskiy speaks to soldiers during his visit to military base outside Kyiv, Ukraine, Monday, Sept. 30, 2019. Ukraine's president told media his country won't be pressured into opening an investigation into Democratic presidential candidate Joe Biden and his son. A Ukrainian prosecutor announced he was reopening probes into a number of cases, including one involving a company where Biden served on the board

Former Vice President and Democratic presidential candidate Joe Biden speaks during a gun safety forum Wednesday, Oct. 2, 2019, in Las Vegas

Ukrainian prosecutor Ruslan Ryaboshapka told reporters in Kyiv that prosecutors are auditing all the cases that were closed or dismissed by former prosecutors, including several related to Mykola Zlochevsky, owner of the gas company Burisma that hired Hunter Biden in 2014, at the same time his father was leading the Obama administration´s diplomatic dealings with Kyiv.

Though the timing raised concerns among anti-corruption advocates, there has been no evidence of wrongdoing by either the former vice president or his son.

'We are now reviewing all the cases that were closed or split into several parts or were investigated before, in order to be able to rule to reverse those cases where illegal procedural steps were taken,' Ryaboshapka said.

Asked by The Associated Press about Trump´s comment Thursday that the U.S. has an 'absolute right' to ask foreign leaders to investigate corruption cases, Zelensky said that Ukraine is 'open' and that all the cases under investigation are 'transparent.'

The Prosecutor General´s Office later said that among the cases they are reviewing, there are 15 where Zlochevsky is mentioned. None of the Zlochevsky-related cases has been revived yet, they said.

They did not specify how many, if any, were related to Hunter Biden´s work at Burisma.

Ryaboshapka was mentioned in the July 25 call between Trump and Ukrainian President Volodymyr Zelensky, who assured Trump that Ryaboshapka was 'his man' and that he would resume investigations into Burisma.

The prosecutor general insisted on Friday that he did not feel any pressure over the Burisma case.

'Not a single foreign or Ukrainian official or politician has called me or tried to influence my decisions regarding specific criminal cases,' he said.

A whistleblower last month revealed that Trump in a phone call asked Zelensky to resume the probe into Joe Biden and his son. The July 25 call has since triggered an impeachment inquiry against Trump.

The newly-announced action in Ukraine comes amid additional revelations about Trump administration efforts to push an investigation – including by leveraging a presidential visit.

Trump 's aides told the Ukrainian president to investigate Hunter Biden and the 2016 election if he wanted a visit to Washington, 23 pages of texts released by Adam Schiff and House Democrats revealed.

Kurt Volker, Trump's former envoy to Ukraine, told an aide to Zelensky that the U.S. would only 'nail down' a date once the Ukrainian president promised to 'get to the bottom of what happened' - reference to an unproven theory Joe Biden, as vice president, interfered in a Ukrainian investigation into a gas company that had Hunter Biden on its board.

Scroll down to read all 23 pages of texts

Volker sent the text, released late Thursday night, just hours before the phone call between Trump and Zelensky that sparked the impeachment probe.

The tranche of texts - handed over by Volker as part of his testimony to lawmakers in their impeachment inquiry of Trump - revealed the pressure the president's aides put on the Ukraine to give credence to an unsubstantiated theory of corruption on the part of Joe Biden, the frontrunner for the Democratic presidential nomination.

Donald Trump (pictured in Florida yesterday) admits he told Zelensky to investigate the Bidens, but has repeatedly denied pressuring Ukraine with a 'quid pro quo'

House Intelligence Committee Chairman Adam Schiff released the texts late Thursday

Charge d'affaires at the U.S. Embassy in Ukraine William Taylor voiced concerns about pressuring Ukraine, writing: 'This is my nightmare scenario'

U.S. Ambassador to the European Union Gordon Sondland, who was appointed by Trump to his job, is one of key players in the text exchanges

Biden is not mentioned by name in them but the subtext is clear and Democrats used the texts to argue they show Trump put pressure on a foreign power to target a domestic political rival.

Mentioned in the texts is Rudy Giuliani, Trump's personal attorney who has been one of the biggest advocates of the Biden theory and, at one point, had talked of going to the Ukraine to investigate it.

'It's been mischaracterized,' he told Fox News Thursday night of the texts.

Zelensky's government ultimately never released the statement on the 2016 election and Burisma Holdings, the Ukrainian gas company where Hunter Biden sat on the board, that the Trump aides pushed for.

But such a statement would have given the president political fire to use against his opponent without having his fingerprints on its origins.

Scroll down to read all 23 pages of texts

Trump argued Friday morning his target was corruption, not the Bidens.

Trump admits he told Zelensky to investigate the Bidens, but has repeatedly denied pressuring Ukraine or offering a quid pro quo.

On Friday morning, after the texts had been released, the president argued he was fighting 'corruption' and not conducting a political campaign against the Biden.

The Players in the Texts Ambassador Kurt Volker: former special representative for Ukraine Negotiations; Volker testified for eight hours behind closed doors to lawmakers on Thursday and provided the text messages William B. Taylor: Charge d'Affaires at the U.S. Embassy in Ukraine; a career State Department employee, he was the top American diplomat in Ukraine after the Trump administration forced out Ambassador Marie Yovanovitch Gordon Sondland: U.S. Ambassador to European Union; he's also a prominent Republican fundraiser and donor who gave $1 million to Trump's inauguration committee; Trump appointed him to his ambassador job Andrey Yermak: top aide to Ukrainian President Volodymyr Zelensky Rudy Giuliani: Personal lawyer to President Donald Trump Advertisement

'As President I have an obligation to end CORRUPTION, even if that means requesting the help of a foreign country or countries. It is done all the time. This has NOTHING to do with politics or a political campaign against the Bidens. This does have to do with their corruption!,' he wrote on Twitter.

However, Democrats will seize on the new messages as evidence that Trump's aides explicitly linked Ukraine's investigation to a visit to Washington.

The texts also reveal that U.S. Ambassador William Taylor voiced concerns about pressuring Ukraine, calling it 'my nightmare scenario.'

Volker, who resigned from his part time State Department job last week, gave evidence to lawmakers in an eight-hour session behind closed doors on Thursday.

'Heard from White House - assuming President Z convinces trump he will investigate / 'get to the bottom of what happened' in 2016, we will nail down date for visit to Washington. Good luck!' Volker wrote in the July 25 message - sent before Trump's phone call with Zelensky.

He sent the text to Andrey Yermak, an aide of Zelensky's who later responded that the 'phone call went well'.

Days earlier, on July 19, after he had breakfast with Giuliani, Volker told Sondland the 'most important thing' in the call was for Zelensky to 'say that he will help investigation'.

Volker and fellow diplomats also discussed a draft statement in which Ukraine would announce a probe into Burisma Holdings and Joe Biden's request - made in 2016 when he was vice president - that the Ukrainian government remove a prosecutor who was accused of not prosecuting corruption cases in the country. The International Monetary Fund and European diplomats also pushed for the prosecutor to be ousted.

Trump argued Friday morning his target was corruption, not the Bidens

Kurt Volker sent this text, released by House Democrats in a 23-page tranche last night, just hours before the phone call between Trump and Zelensky which is at the center of the impeachment probe

Trump's former envoy to Ukraine Kurt Volker departs following his closed-door testimony yesterday during which he handed over a tranche of texts which were released last

However, on August 10 Yermak demanded that Zelensky's trip to Washington D.C. be confirmed before they released a statement, saying 'it will be logic [sic] to do after we receive a confirmation of date'.

'Once we have a date we will call for a press briefing, announcing upcoming visit and outlining vision for the reboot of US-UKRAINE relationship , including among other things Burisma and election meddling in investigations,' Yermak wrote.

'Sounds great!' texted Volker.

U.S. Ambassador to the European Union Gordon Sondland, who was appointed by Trump to his job, is one of key players in the text exchanges

Charge d'affaires at the U.S. Embassy in Ukraine William Taylor voiced concerns about pressuring Ukraine, writing: 'This is my nightmare scenario'

Trump and his allies claim Biden, when he was vice president, pressured the Ukrainian government to fire the country's top prosecutor to protect his son Hunter and Burisma Holdings, which was accused of corrupt practices.

There has been no evidence of illegal activity or wrongdoing in Ukraine by the Bidens and there are reports Trump's own advisers warned him the theory was incorrect.

Trump has demanded a probe into the Bidens anyway.

Ukraine's new top prosecutor said this week his office was reviewing a number of cases related to Burisma.

However, he said he was not aware of any wrongdoing by Hunter Biden and had not been contacted by any foreign lawyers about the case.

The proposed investigation would also have looked at unsubstantiated allegations that Ukraine meddled in the 2016 race on behalf of Hillary Clinton.

According to the texts, Volker, Sondland and William 'Bill' Taylor, the charge d'affaires at the U.S. embassy in Ukraine, discussed the statement Zelensky would issue in support of the investigation.

House Intelligence Committee Chairman Adam Schiff released the texts late Thursday

Donald Trump (pictured in Florida yesterday) admits he told Zelensky to investigate the Bidens, but has repeatedly denied pressuring Ukraine with a 'quid pro quo'

The 23 pages of texts released by Democratic House committee chairmen last night

Rudy Giuliani is mentioned several times in the text exchanges

As the negotiations progressed, Sondland said Trump 'really wants the deliverable,' referring to Ukraine's commitment to conduct the investigation.

Then, Trump froze nearly $400million in U.S. military assistance to Ukraine shortly before speaking to Zelensky.

'Need to talk with you,' Yermak wrote to Volker on August 28 when the news of freeze broke.

Taylor, the seasoned top diplomat in the Ukrainian embassy and a career State Department employee, conveyed his concerns and questioned whether the money was being withheld until Ukraine agreed to Trump's demand.

'Are we now saying that security assistance and WH meeting are conditioned on investigations?' he wrote on September 1.

Sondland, a Trump appointee, quickly moved the conversation from texting to a phone call.

'Call me,' Sondland replied.

But as Trump never committed to a meeting with Zelensky and U.S. aid to the country was on hold, the texts reflected diplomatic concerns.

Taylor had earlier warned Sondland earlier that Zelensky was 'sensitive about Ukraine being taken seriously, not merely as an instrument in Washington domestic, re-election politics.'

'The message to the Ukrainians (and Russians) we send with the decision on security assistance is key. With the hold, we have already shaken their faith in us. Thus my nightmare scenario,' Taylor wrote to Sondland on September 9.

'As I said on the phone, I think it's crazy to withhold security assistance for help with a political campaign,' he added.

'The president has been crystal clear no quid pro quo's of any kind,' Sondland replied. 'The president is trying to evaluate whether Ukraine is truly going to adopt the transparency and reforms that president Zelensky promised during his campaign I suggest we stop the back and forth by text.'

Giuliani appeared numerous times in the 23-page tranche, put in touch with Yermak by Volker in a text on July 19.

Volker also sought Giuliani's advice on the statement that Zelensky should make about the investigation.

'Can we all get on the phone to make sure I advise Z correctly as to what he should be saying? Want to make sure we get this done right,' Volker wrote on August 9.

'Yes can you call me now going to a fundraiser at 12:30,' Giuliani responded.

The Ukrainian government ultimately never released the statement.

The release of the text messages came on the same day Volker that spoke for more than eight hours to House lawyers.

Adam Schiff, the chairman of the House intelligence committee, released the texts late Thursday night.

Ukrainian leader Volodymyr Zelensky, pictured at a press conference in Kiev on Tuesday, spoke to Donald Trump by phone on July 25

Trump has pushed for an investigation of the unproven theory that Joe Biden, when he was vice president, pressured the Ukrainian government to fire the country's top prosecutor to protect his son Hunter and Burisma Holdings, which was accused of corrupt practices

In a joint letter with fellow committee chairmen Elijah Cummings and Eliot Engel, Schiff and his colleagues accused the Trump administration of 'unethical and unpatriotic' behavior.

'This is not normal or acceptable. It is unethical, unpatriotic, and wrong,' the three chairmen wrote.

'American Presidents should never press foreign powers to target their domestic political rivals.

'Engaging in these stunning abuses in broad daylight does not absolve President Trump of his wrongdoings - or his grave offenses against the Constitution.

'The excerpts we are providing are still only a subset of the full body of materials, which we hope to make public after a review for personally identifiable information.'

The July 25 call between Trump and Zelensky became public after a whistleblower went to authorities with concerns about Trump's behavior, triggering the impeachment probe.

The White House released a partial transcript of the call, showing that Trump asked Ukraine for a 'favor' by launching an investigation.

'I would like to have the Attorney General call you or your people and I would like you to get to the bottom of it,' Trump told Zelensky.

Zelensky, for his part, promised that 'all the investigations will be done openly and candidly'.

Thursday, Trump refused to back down on his claims that Ukraine and even China should investigate the Bidens.

'I would say that President Zelensky, if it were me, I would recommend that they start an investigation into the Bidens. Because nobody has any doubt that they weren't crooked,' Trump said.

'I would think if they were honest about it they'd start a major investigation into the Bidens. It's a very simple answer.

'Likewise China should start an investigation into the Bidens. Because what happened to China is about as bad as what would happen to Ukraine.'

Asked if he had requested President Xi to help investigate the Biden family, Mr Trump said: 'I haven't but clearly it's something we should start thinking about.'

Trump doubled down on his comments in a tweet, saying: 'As the President of the United States, I have an absolute right, perhaps even a duty, to investigate, or have investigated, CORRUPTION, and that would include asking, or suggesting, other Countries to help us out!'