President Donald Trump says he discussed political rival Joe Biden with the president of Ukraine — a phone call reportedly at the heart of a whistleblower complaint that has led to the launch of formal impeachment proceedings in the House — for one reason: a desire to root out corruption.

The former vice president, Trump said, wielded his influence to benefit his son Hunter’s private-sector work in Ukraine. But despite Trump's continued claims, there's no evidence of wrongdoing on the part of either Biden.

"What Joe Biden did for his son, that’s something they should be looking at," Trump told reporters Tuesday, deflecting questions about the renewed push by House Democrats for impeachment proceedings in the wake of the revelations surrounding his dealings with Ukraine, which include reports that he pressured Ukraine's leader to probe Biden and his family while that country was awaiting U.S. aid he'd delayed.

Here's what we know about Biden's actions as vice president with regard to Ukraine, Trump's accusations and the phone call, and Trump's own dealings with the country's leader.

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Biden's anti-corruption work in Ukraine

As vice president, the elder Biden lead the U.S. diplomatic efforts to bolster the country’s fledgling democracy and root out corruption after mass protests ousted the country’s pro-Russia president, Viktor Yanukovych.

Biden spoke frequently with Ukrainian leaders and in April 2014, he traveled to Ukraine, bringing financial support and warning the Russians — who had recently annexed Crimea — to stop intervening in Ukrainian sovereignty.

Hunter Biden and Joe Biden attend the World Food Program USA's Annual McGovern-Dole Leadership Award Ceremony at Organization of American States on April 12, 2016 in Washington, DC. Teresa Kroeger / Getty Images file

In May 2014, Hunter Biden was hired by a Ukrainian gas company, Burisma Holdings, as a board member reportedly making $50,000 a month. He stopped working with the company earlier this year.

The company had ties to Yanukovych, raising eyebrows among White House aides and others who saw potential for a conflict of interest. The Obama White House said at the time that the younger Biden was a private citizen, and that there was no conflict of interest.

Trump's quid pro quo claims

Trump, whose July phone conversation with Ukrainian President Volodymyr Zelenskiy was reportedly so unusual it triggered a whistleblower complaint, said Sunday ahead of his departure for an event in Texas that he discussed with the Ukrainian leader "the fact that we don’t want our people like Vice President Biden and his son creating the corruption already in the Ukraine."

NBC News has not confirmed that Ukraine is at the center of the whistleblower issue.

Trump reiterated this version of events to reporters once he arrived in Houston.

"He said, 'I’m not going to give billions of dollars to Ukraine unless they remove this prosecutor.' And they removed the prosecutor supposedly in one hour," Trump claimed, referring to Biden. "And the prosecutor was prosecuting the company of the son and the son. He just shouldn’t have said that. Now, as far as my conversation, it was perfect. It was a perfect conversation."

On Monday, he reiterated this claim.

"It was a perfect call. There was no quid pro quo, unlike Biden," Trump said.

But the revelation of the whistleblower complaint from a member of the U.S. intelligence committee, first reported in The Washington Post, reportedly involving the call came after a monthslong effort by the president's personal attorney, Rudy Giuliani, to get Ukraine to probe the Bidens — an effort aided by the State Department.

Both Trump and Giuliani have alleged that Biden used the prospect of U.S. financial support to pressure the Ukrainian government to fire its top prosecutor in 2016, because the prosecutor, Viktor Shokin, was investigating the gas company Burisma, and allegedly, Hunter.

Shokin was widely believed to be soft on corruption, however, and the United States and other Western countries had called for his removal. The country's Parliament ultimately voted to remove Shokin.

Biden has taken credit for getting the prosecutor removed, boasting about it as a win for anticorruption in the country.

But there's little evidence he acted to help his son: Earlier this year, Bloomberg News, citing documents and an interview with a former Ukrainian official, reported the Burisma investigation had been dormant for more than a year by the time Biden called for the crackdown on corruption. The then-Ukrainian prosecutor general told the news agency he found no evidence of wrongdoing by Biden and his son. And PolitiFact reported it found no evidence to "support the idea that Joe Biden advocated with his son's interests in mind."

Additionally, the most recent former prosecutor general of Ukraine, Yuriy Lutsenko, told Bloomberg he had no evidence of wrongdoing by either Biden.

Other investigations into Burisma's oligarch owner, Mykola Zlochevsky, proceeded, and The New York Times reported Sunday that former associates of the vice president have said Biden did not try to stop them.

Trump's dealings with Ukraine

A week before the president's phone call with the Ukrainian leader, Trump instructed his acting chief of staff to freeze about $400 million in security and military aid, two administration officials told NBC News. This timeline was first reported by the Washington Post.

The administration official who directed the State Department to withhold the aid to Ukraine was acting chief of staff Mick Mulvaney, according to a senior Democratic aide who was briefed by the State Department last week.

According to a memo summarizing the call released by the White House, Trump stressed how "good" the United States had been to Ukraine.

"I will say that we do a lot for Ukraine. We spend a lot of effort and a lot of time. Much more than the European countries are doing and they should be helping you more than they are," Trump said. "The United States has been very, very good to Ukraine. I wouldn't say that it's reciprocal necessarily because things are happening that are not good but the United States has been very, very good to Ukraine."

Then he asks Zelenskiy to look into the Bidens.

"There's a lot of talk about Biden’s son, what Biden stopped the prosecution and a lot of people want to find out about that, so whatever you can do with the attorney general would be great. Biden went around bragging that he stopped the prosecution, so if you can look into it. ... It sounds horrible to me," Trump said, according to the the White House notes of the call.

Trump also says he wants Zelenskiy to meet with Giuliani and noted that he "heard the prosecutor was treated very bad and he was a very fair prosecutor," according to the memo.

In fact, Shokin, the prosecutor in question, was widely believed to be corrupt, and Bloomberg News has reported that his investigation into Burisma was dormant by the time Biden called for his resignation.

Pressed Tuesday about the call — prior to the public release of the summary — Trump said he did it in protest of other countries' actions.

"My complaint has always been — and I'd withhold again, and I'll continue to withhold until such time as Europe and other nations contribute to Ukraine, because they're not doing it. It's the United States. We're putting up the bulk of the money, and I'm asking why is that?" Trump said, referring to the international aid that's been sent to bolster Ukraine and its fledgling democracy against Russian aggression.

This is not true: The European Union put up $16.5 billion in financial aid, according to a fact sheet from the E.U.'s diplomatic arm. The International Monetary Fund said it would put forward at least $14 billion in a bailout as well.

Biden's response to Trump's Ukraine conspiracy theory

“Trump's doing this because he knows I'll beat him like a drum and he's using the abuse of power and every element of the presidency to try to do something to smear me," Biden said this weekend, telling reporters that Trump had abused his power and "violated the Constitution."

Biden also said he's "never spoken to my son about his overseas business dealings."

Still, in a July profile in The New Yorker, Hunter Biden recalled a brief conversation with his father about his work in Ukraine: "As Hunter recalled, his father discussed Burisma with him just once: “Dad said, ‘I hope you know what you are doing,’ and I said, ‘I do.’"

Biden said Tuesday he'd support impeachment if the president didn't cooperate with congressional oversight of the whistleblower complaint. Democrats had decried the administration for failing to provide the complaint to Congress after the intelligence community's inspector general deemed the matter an "urgent concern" that he was required by law to turn over to the congressional intelligence committees.

“If the president does not comply with such a request from the Congress, if he continues to obstruct Congress and flout the law, Donald Trump will leave Congress, in my view, no choice but to initiate impeachment. That would be a tragedy, but a tragedy of his own making," Biden said.

Hours after House Speaker Nancy Pelosi, D-Calif., announced a formal impeachment inquiry Tuesday evening, the Trump administration reversed course on the whistleblower complaint. The White House is now preparing to turn over the complaint to Congress by Thursday, according to a senior administration official.

That official tells NBC News the complaint will first undergo a classification review.