Trump responds to impeachment threat amid fresh push to remove him over Ukraine phone call revelations

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.

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.

"This is requesting assistance from a foreign government to tarnish your political rival and opening the door to outside interference in our politics and elections," David Kramer, a former State Department official during the George W Bush administration, told the Washington Post.