Democratic calls to impeach President Donald Trump are gathering pace after it emerged he withheld aid to Ukraine, pressing it to investigate his would-be White House challenger Joe Biden.
The House of Representatives' Democratic leader, Speaker Nancy Pelosi, is meeting party members on Tuesday to consider impeachment.
Mr Trump has acknowledged freezing the aid to Ukraine but denied wrongdoing.
Only two US presidents have ever been impeached.
At the United Nations General Assembly in New York City on Tuesday, Mr Trump said he only froze military aid to Ukraine because he wanted European countries to contribute money, too.
The Republican president also acknowledged pressuring newly elected Ukrainian President Volodymyr Zelensky during a phone call on 25 July to investigate US Democratic presidential candidate Joe Biden.
He told reporters "there was pressure put on, in respect to Joe Biden. What Joe Biden did for his son, that's something they should be looking at."
Mr Trump's remarks came after US media reported that days before his phone call with Mr Zelensky, Mr Trump instructed his acting chief of staff, Mick Mulvaney, to withhold nearly $400m in military aid for Ukraine.
But the US president insisted on Tuesday that nothing untoward happened during the "perfect call".
Mr Trump and his conservative allies have pointed out that Joe Biden, while US vice-president, threatened in 2016 to withhold aid to Ukraine unless it fired a top prosecutor whose office had opened an investigation into a natural gas company where Mr Biden's son, Hunter Biden, was a board member.
Other Western officials had also called for the same prosecutor to be removed for being soft on corruption. Ukraine's current prosecutor, Yuriy Lutsenko, told Bloomberg News in May he had no evidence of wrongdoing by Mr Biden or his son.
Congressional Democrats are demanding a transcript of the Trump-Zelensky phone call, which the White House has declined to release.