WASHINGTON -- From front-row seats at the White House, two government officials are providing impeachment panels vivid testimony of the Trump administration's efforts pushing Ukraine to investigate Democrats and Joe Biden.

According to transcripts released Friday in the impeachment inquiry of President Donald Trump, Fiona Hill, a former White House Russia adviser, and Lt. Col. Alexander Vindman, an Army officer assigned to the National Security Council, both described firsthand views of extraordinary scenes during a single day of meetings with Ukraine officials at the White House.

In one, Trump's national security adviser John Bolton "immediately stiffened" as Ambassador Gordon Sondland "blurted out" that he had worked out a trade -- Ukrainians' probe for an Oval Office welcome -- with Trump's acting chief of staff, Mick Mulvaney.

"Well, we have an agreement with the chief of staff for a meeting if these investigations in the energy sector start,"Hill recalled -- a reference to the firm, Burisma, where Biden's son was on the board.

And then? Hill said Bolton abruptly ended the meeting.

In another episode in the Ward Room at the White House, Vindman testified that Sondland told Ukrainians they would need to investigate the Bidens if they hoped to have that coveted meeting with Trump.

"He was calling for something, calling for an investigation that didn't exist into the Bidens and Burisma," Vindman said. "The Ukrainians would have to deliver an investigation into the Bidens."

Into the Bidens? the investigators pressed.

"To the best of my recollection, yes," he said. "My visceral reaction to what was being called for suggested that it was explicit. There was no ambiguity."

Both officials testified behind closed doors last month in the probe. The hundreds of pages of transcripts showed a deeper reach into the White House ahead of next week's public hearings.

Vindman alerted superiors on two occasions, including after he listened to the July call in which Trump personally appealed to Ukrainian President Volodymyr Zelenskiy to investigate political rival Biden and the outlier theory of a Ukrainian role in the 2016 U.S. presidential election.

A whistleblower's complaint about that call triggered the impeachment probe.

Trump insisted earlier Friday he has not been damaged by testimony and Republicans complain the witnesses generally are relying on secondhand accounts of the events central to the probe.

Speaking to reporters as he left on a campaign trip to Atlanta, Trump said he was "not concerned about anything" that has been disclosed so far.

But the new testimony, particularly the day of meetings July 10 at the White House, has become pivotal. It puts Mulvaney more directly involved in the shadow diplomacy being run through Rudy Giuliani, the president's personal attorney, and Sondland, the wealthy businessman-turned-ambassador to the European Union.

After Bolton left the one meeting, he told Hill to follow the group into the next and report back to him.

She testified at the second White House meeting, Sondland "as I came in, was talking about how he had an agreement with Chief of Staff Mulvaney for a meeting with the Ukrainians if they were going to go forward with investigations."

She said she heard Sondland mention Burisma as part of this exchange. When she reported it back to Bolton, he called it a "drug deal" and told her to report it to the National Security Council lead counsel, John Eisenberg.

She testified:

"This is a direct quote from Ambassador Bolton: 'You go and tell Eisenberg that I am not part of whatever drug deal Sondland and Mulvaney are cooking up on this, and you go and tell him what you've heard and what I've said."'

Republican Rep. John Ratcliffe, a Texas Republican, sought to portray Trump's request for a favour in his phone call with the Ukrainian president as falling short of a demand.

But Vindman disagreed.

"When the president of the United States makes a request for a favour, it certainly seems, I would take it as a demand," he retorted.

Vindman, a veteran of the Iraq War, then added: "Congressman, as a military officer if my superiors tell me to do something, I take that not as a request , I take that as a demand."

At one point in Vindman's testimony, his lawyer objected to questions from Republicans he believed were intended to draw out the identity of the whistleblower who filed the initial complaint.

Vindman had already said in an opening statement that he was not the whistleblower and did not know who was. His lawyer, Michael Volkov, said his client would not answer questions about how many people he had told about his concerns.

Pressed repeatedly, Volkov said, "He tells you he's not the whistleblower, OK? He says he feels uncomfortable about it. Try and respect his feelings at this point."

A person then identified only as "voice" interjects: "We're uncomfortable impeaching the president."

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Associated Press writers Colleen Long, Mike Balsamo, Matthew Lee, , Matthew Daly, Laurie Kellman and Jill Colvin contributed to this report.