A senior US diplomat has testified that the Trump administration threatened to withhold military aid from Ukraine unless it agreed to investigate Mr Trump’s leading US presidential rival.
Bill Taylor, the top US diplomat in Ukraine, told impeachment hearings he had a “clear understanding” aid would be withheld pending an investigation.
Mr Trump denies there was any threat.
Public impeachment hearings will begin next Wednesday, with Mr Taylor set to be the first witness called.
Mr Taylor testified in closed door impeachment hearings last month, and a transcript of his evidence was released to the public on Wednesday.
He told a Congressional committee that two state department officials said Mr Trump would not “sign a check” for nearly $400m (£311m) in US military aid until Ukrainian officials announced an investigation into Democratic presidential contender and former Vice-President Joe Biden.
Mr Biden’s son Hunter Biden previously sat on the board of the Ukrainian oil company Burisma. President Trump has claimed without evidence that Joe Biden used his position as vice-president to quash an investigation into Burisma.
Mr Taylor also told the Congressional committee that Mr Trump’s personal lawyer, Rudy Giuliani, was behind the drive to get Ukraine to announce an investigation into the Bidens.
Mr Taylor’s testimony followed evidence from Gordon Sondland, an ally of President Trump who is the US ambassador to the European Union, who told the impeachment hearings that he informed a Ukrainian official of a quid pro quo – US military aid in exchange for an investigation announcement. Mr Sondland testified that a White House visit for the Ukrainian president was also part of the deal.
Mr Sondland had returned to Congress to revise earlier testimony, in which he denied that any preconditions had been placed on the delivery of aid.
Critics of Mr Trump say that any quid pro quo would be a clear violation of president ethics, because it uses the power and office of the presidency in an attempt to damage a domestic political rival. Mr Trump denies that there was any quid pro quo.
Also on Thursday, the Washington Post and the New York Times reported that President Trump asked that the attorney general, William Barr, hold a news conference to declare that the president had broken no laws during his call with the Ukrainian president – the very call that led to a whistleblower complaint against Mr Trump.
Congressional Democrats announced on Wednesday that the first public hearings of the inquiry would take place next Wednesday. Three state department officials, including Mr Taylor, will testify first. So far, lawmakers from three key Congressional committees have heard from witnesses behind closed doors.
The Capitol Hill hearings will be broadcast live, with both Democratic and Republican lawmakers questioning witnesses.