The House of Representatives on Saturday also released a transcript of an earlier closed-door deposition by Tim Morrison
The phone call between US President Donald Trump and his Ukrainian counterpart at the centre of Congress' impeachment investigation was "inappropriate," a foreign policy aide to Vice President Mike Pence told lawmakers, according to a transcript released on Saturday.
Jennifer Williams, who was listening to the call on July 25, testified that Trump's insistence that Ukraine carry out politically sensitive investigations "struck me as unusual and inappropriate."
The House of Representatives on Saturday also released a transcript of an earlier closed-door deposition by Tim Morrison, a White House aide with the National Security Council focusing on Europe and Russia policy.
"I was not comfortable with any idea that President Zelenskiy should allow himself to be involved in our politics," said Morrison, who also was on the call.
Trump's call is at the heart of the Democratic-led inquiry into whether the Republican president misused US foreign policy to undermine former US Vice President Joe Biden, one of his potential opponents in the 2020 election.
Morrison declined to say he thought the call was illegal or improper, stressing instead that he thought it would leak, and damage relations with Ukraine.
In a disclosure that drew the most attention in the first public hearing last week, acting ambassador to Ukraine William Taylor pointed to Trump's keen interest in getting the eastern European ally to investigate Biden and reiterated his understanding that $391 million in US security aid was withheld from Kiev unless it cooperated.
Morrison said he had reviewed Taylor's testimony and did not dispute it on any significant points.
House investigators on Saturday also heard closed-door testimony from a White House budget official about the holdup of military aid to Ukraine. Mark Sandy, a career official of the Office of Management and Budget, is the first person from OMB to testify before the inquiry after three political appointees defied congressional subpoenas to appear.
Democratic Representative Jamie Raskin, a member of the Judiciary and Oversight Committees, said Sandy was brought in to shed light on whether military aid was held up for political reasons.
"This is a technical part of our investigation," Raskin told reporters outside the interview room. "We want to know exactly how the president translated his political objective to shake down the Ukrainian government for the favours he wanted (into) the budget process."
On Friday, Trump used Twitter to criticize a former US ambassador to Ukraine, Marie Yovanovitch, while she was testifying to an impeachment hearing, an extraordinary moment that Democrats said amounted to witness intimidation. Trump defended his attack on Yovanovitch, saying he had the right to free speech.
Yovanovitch, a career diplomat, testified on the second day of televised impeachment hearings, which will resume next week.
While Yovanovitch's testimony dominated headlines on Friday, a closed-door deposition lawmakers held later in the day with David Holmes, a US embassy official in Kiev, could prove more consequential.
Holmes told lawmakers he overheard a phone call between Trump and Gordon Sondland, the US ambassador to the European Union, in which the president inquired about Ukraine's willingness to carry out investigations of Biden and his son.
The phone call occurred on July 26, one day after the now-infamous phone conversation between Trump and Zelenskiy.
"So, he's gonna do the investigation?" Trump asked Sondland, referring to Zelenskiy, according to Holmes' testimony.
"He's gonna do it," replied Sondland, adding the Ukrainian president would do "anything you ask him to," according to Holmes.
The testimony by Holmes, an aide to Taylor, ties Trump more directly to a pressure campaign in Ukraine to investigate the Bidens led by Trump's personal lawyer Rudy Giuliani.
Holmes' statement appears to contradict Sondland's previous sworn testimony about his interactions with Trump, in which he did not mention his July 26 phone call with the president.
Sondland, who has already revised his testimony once, is scheduled to testify publicly on Wednesday.
Representative Eric Swalwell, a Democrat on the House Intelligence Committee, told reporters on Saturday that House leaders were considering bringing Holmes in for a public hearing.