WASHINGTON • An official on the White House's National Security Council (NSC) said he heard the US ambassador to the European Union explicitly press Ukrainian officials to investigate Mr Joe Biden and his son, according to a transcript released last Friday by Democrats leading the impeachment probe of President Donald Trump.
US Army Lieutenant-Colonel Alexander Vindman, a Ukraine expert on the NSC, said Ambassador Gordon Sondland made it clear in a July 10 meeting at the White House that the investigations of the Bidens and Ukrainian gas company Burisma would have to be opened for Ukraine President Volodymyr Zelensky to get an Oval Office meeting with Mr Trump.
"He was calling for something, calling for an investigation that didn't exist into the Bidens and Burisma," Lt-Col Vindman said. "My visceral reaction to what was being called for suggested that it was explicit. There was no ambiguity."
His comments could give Democrats further ammunition in their push to determine whether Mr Trump misused US foreign policy to pressure Ukraine into carrying out a corruption probe into Democrat Joe Biden, a potential rival in the 2020 presidential election.
The inquiry enters a critical phase next week when House committees hold impeachment hearings in public.
Lt-Col Vindman was among the US officials in the White House Situation Room monitoring Mr Trump's call two weeks later on July 25 with Mr Zelensky, a main focus of the impeachment probe.
Lt-Col Vindman said he had no doubt that Mr Trump demanded that Ukraine open the investigations in return for an Oval Office visit for the Ukrainian leader.
He told lawmakers that he believes ties between the US and Ukraine have been damaged by the administration's actions. "It undercuts US resolve to support Ukraine and certainly puts a question into their mind whether they in fact have US support," he said.
His account of the July 10 meeting at the White House was corroborated by Ms Fiona Hill, the former senior director for European and Russian affairs on Mr Trump's NSC.
Ms Hill testified that she heard Mr Sondland bring up Burisma at the meeting, according to a separate transcript of her testimony released last Friday.
Also on Friday, attorney Charles Cooper who represents Mr Trump's former national security adviser, Mr John Bolton, sent a letter to House lawmakers that suggested that Mr Bolton knows about "many relevant meetings and conversations" concerning Mr Trump's actions towards Ukraine.
Mr Cooper tucked the tantalising assertion into a letter to the chief House lawyer in response to committee chairmen who have sought Mr Bolton's testimony in their impeachment inquiry but expressed unwillingness to go to court to get an order compelling it.
Mr Cooper did not elaborate on what meetings or conversations he was referring to, leaving it to House Democrats to guess at what he might know.
But the hints about what Mr Bolton might be able to add came as new details emerged from the impeachment inquiry about how an effort by Mr Trump's allies to use the US' relationship with Ukraine to accomplish the President's political goals opened a bitter rift inside the White House.
With public hearings getting under way, House Republicans made a move to bolster their response to the impeachment probe.
House Minority Leader Kevin McCarthy announced that Representative Jim Jordan, an aggressive Trump defender, had been assigned to the House Intelligence Committee.