Donald Trump has insisted he is not taking the threat of impeachment "at all seriously", after effectively admitting he asked a foreign leader to investigate potential 2020 presidential election rival Joe Biden.

Asked by a reporter how seriously he was taking the prospect, as he arrived at the United Nations in New York, the president said: "Not at all seriously."

The claim comes as Democrats in Congress have once again called for impeachment proceedings against the president, and as the White House has pushed back on releasing whistle blower documents related to a call between Mr Trump and Ukrainian president Volodymyr Zelensky, in which the American leader reportedly pushed his Ukrainian counterpart to reopen an investigation into a gas tycoon with connections to Mr Biden's son, Hunter.

The US, in the months after that call, withheld around $250 million in military funding, leading to speculation that Mr Trump was using his power as president to try and force the Ukrainian to investigate a potential political rival.

"We're supporting a country. We want to make sure that country is honest...it's very important to talk about corruption. If you don't talk about corruption, why would you give money to a country that you think is corrupt?" Mr Trump said Monday in New York.

Ukraine Elections 2019 in pictures Show all 26 1 /26 Ukraine Elections 2019 in pictures Ukraine Elections 2019 in pictures Volodymyr Zelenskiy, centre right, and his wife Olena Zelenska, greet supporters after exit polling gave the comedian a commanding lead AP Ukraine Elections 2019 in pictures Outgoing Ukrainian President Petro Poroshenko raises his hand with his wife Maryna at his party headquarters in Kiev AFP/Getty Images Ukraine Elections 2019 in pictures Ukrainian presidential candidate Volodymyr Zelenskiy reacts following the announcement of the first exit poll REUTERS Ukraine Elections 2019 in pictures Comedian and leading Ukrainian presidential candidate Volodymyr Zelenskiy plays ping pong with a journalist at his election night gathering in Kiev, Ukraine. If no candidate receives more than 50% of the vote, the top two vote-getters will face off in a second-round election on April 21 Getty Ukraine Elections 2019 in pictures Election officials count ballots at a polling station in Kiev during the first round of Ukraine's presidential election, AFP/Getty Ukraine Elections 2019 in pictures People walk in front of St. Sophia Cathedral in Kiev during Ukraine's presidential election AFP/Getty Ukraine Elections 2019 in pictures Ukrainian servicemen sit in a truck to head to a polling station, near the front line with pro-Russian separatists, near Butivka, Donetsk region AFP/Getty Ukraine Elections 2019 in pictures Ukrainian citizens living in Kyrgyzstan vote in Ukraine's presidential election at a polling station in the Ukrainian embassy in Bishke AFP/Getty Ukraine Elections 2019 in pictures Ukrainian citizens living in Kyrgyzstan vote in Ukraine's presidential election at a polling station in the Ukrainian embassy in Bishkek AFP/Getty Ukraine Elections 2019 in pictures Ukrainian citizens living in Kyrgyzstan vote in Ukraine's presidential election at a polling station in the Ukrainian embassy in Bishkek AFP/Getty Ukraine Elections 2019 in pictures Ukrainian citizens living in Kyrgyzstan vote in Ukraine's presidential election at a polling station in the Ukrainian embassy in Bishkek AFP/Getty Ukraine Elections 2019 in pictures A young girl casts the ballot of a man at a polling station in Kiev on the first round of Ukraine's presidential election, on. Exit polls are expected when voting stations close at 8 pm local time (1700 GMT). First preliminary results are expected several hours after. Barring a shock result in which one candidate crosses the 50 percent threshold in the first round, a run-off will be held on April 2 AFP/Getty Ukraine Elections 2019 in pictures Ukrainian comic actor, showman and presidential candidate Volodymyr Zelensky waves in front of voting booths at a polling station during Ukraine's presidential election in Kiev AFP/Getty Ukraine Elections 2019 in pictures Former Ukrainian Prime Minister and presidential candidate Yulia Tymoshenko speaks with the media after casting her ballot at a polling station during Ukraine's presidential election in Kiev AFP/Getty Ukraine Elections 2019 in pictures Former Ukrainian Prime Minister and presidential candidate Yulia Tymoshenko speaks with the media after casting her ballot at a polling station during Ukraine's presidential election in Kiev AFP/Getty Ukraine Elections 2019 in pictures Former Ukrainian Prime Minister and presidential candidate Yulia Tymoshenko speaks with the media after casting her ballot at a polling station during Ukraine's presidential election in Kiev AFP/Getty Ukraine Elections 2019 in pictures Ukrainian comic actor, showman and presidential candidate Volodymyr Zelensky casts his ballot at a polling station during Ukraine's presidential election in Kiev AFP/Getty Ukraine Elections 2019 in pictures Ukrainian comic actor, showman and presidential candidate Volodymyr Zelensky gestures in front of voting booths at a polling station during Ukraine's presidential election in Kiev AFP/Getty Images Ukraine Elections 2019 in pictures Ukrainian comic actor, showman and presidential candidate Volodymyr Zelensky walks with his ballot at a polling station during Ukraine's presidential election in Kiev AFP/Getty Images Ukraine Elections 2019 in pictures A view of the building of the Ukrainian Central Election Commission in Kiev during Ukraine's presidential election. AFP/Getty Ukraine Elections 2019 in pictures Ukrainian President Petro Poroshenko (L) casts his ballot at a polling station in Kiev on the first round of Ukraine's presidential election, The 53-year-old president has positioned himself during the political campaign as the only person able to stand up to the Kremlin and has promised to return Crimea to Ukraine if he is re-elected. AFP/Getty Ukraine Elections 2019 in pictures A voter emerges from the voting booth after filling out her ballot for Ukraine's presidential election in Kiev, Ukraine. If no candidate receives more than 50% of the vote, the top two vote-getters will face off in a second-round election on April 21. Getty Ukraine Elections 2019 in pictures Ukrainian president Petro O. Poroshenko (C), running for re-election, receives his ballot in Ukraine's presidential election on in Kiev, Ukraine. If no candidate receives more than 50% of the vote, the top two vote-getters will face off in a second-round election on April 21 Getty Ukraine Elections 2019 in pictures A woman holds her ballot as she leaves a voting booth at a polling station in Kiev on the first round of Ukraine's presidential election. - Exit polls are expected when voting stations close at 8 pm local time (1700 GMT). First preliminary results are expected several hours after. Barring a shock result in which one candidate crosses the 50 percent threshold in the first round, a run-off will be held on April 21 AFP/Getty Ukraine Elections 2019 in pictures A young girl casts the ballot of a man at a polling station in Kiev on the first round of Ukraine's presidential election. Exit polls are expected when voting stations close at 8 pm local time (1700 GMT). First preliminary results are expected several hours after. Barring a shock result in which one candidate crosses the 50 percent threshold in the first round, a run-off will be held on April 21 AFP/Getty Ukraine Elections 2019 in pictures Ukrainian servicemen queue to cast their ballots at a polling station near the front line line with pro-Russian separatists near Avdiivka, Donetsk region, during the first round of Ukraine's presidential election AFP/Getty

The allegations that Mr Biden had improperly used his position while serving as vice president to benefit his son have largely been discredited, and national security experts have said that Mr Trump's pressure on Ukraine was very inappropriate.

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