The impeachment inquiry is revealing vivid new details about the high-level unease over President Donald Trump's actions toward Ukraine and those of his personal lawyer Rudy Giuliani as the swift-moving probe by House Democrats shows no signs of easing.
The testimony from the witnesses, mainly officials from the State Department and other foreign policy posts, is largely corroborating the account of the government whistleblower whose complaint first sparked the impeachment inquiry, according to lawmakers attending the closed-door interviews.
One witness, former White House aide Fiona Hill, testified that national security adviser John Bolton was so alarmed by Giuliani's back-channel activities in Ukraine that he described him as a "hand grenade who is going to blow everybody up."
Another, career State Department official George Kent, testified Tuesday he was told by administration officials to "lay low" on Ukraine as "three amigos" tied to the White House took over U.S. foreign policy toward the Eastern European ally.
A former top aide to Secretary of State Mike Pompeo is scheduled to testify Wednesday.
Speaker Nancy Pelosi, despite intensifying calls from Trump and Republicans to hold a formal vote to authorize the impeachment inquiry, showed no indication she would do so. She said Congress will continue its investigation as part of the Constitution's system of checks and balances of the executive.
"This is not a game for us. This is deadly serious. We're on a path that is taking us, a path to the truth," Pelosi told reporters after a closed-door session with House Democrats.
WATCH: House Democrats Intensify Trump Inquiry
With Ukraine situated between the United States' Western allies and Russia, Pelosi noted the inquiry raises fresh questions about Trump's relationship with Russian President Vladimir Putin.
"All roads seem to lead to Putin with the president," she said.
Democratic leaders had been gauging support for a vote to authorize the impeachment inquiry after Trump and Republicans pushed them for a roll call. Holding a vote would test politically vulnerable Democrats in areas where the Republican president is popular.
Trump calls the impeachment inquiry an "illegitimate process" and is blocking officials from cooperating.
But several Democratic freshmen who are military veterans or had careers in national security before joining Congress spoke up during the meeting Tuesday, warning Pelosi and her leadership team a vote was unnecessary and would be playing into Republicans' hands, according to a person granted anonymity to discuss the private session.
The inquiry is moving quickly as a steady stream of officials appears behind closed doors this week, some providing new revelations about the events surrounding the July 25 phone call between Trump and Ukrainian President Volodymyr Zelenskiy. It is on that call that Trump urged Zelenskiy to investigate a firm tied to political rival Joe Biden's family and Ukraine's own involvement in the 2016 presidential election.
In a daylong session Tuesday, House investigators heard from Kent, who was concerned about the "fake news smear" against the U.S. ambassador to Ukraine, Marie Yovanovitch, whom Trump recalled in May, according to emails obtained by The Associated Press.
Kent told the lawmakers that he "found himself outside a parallel process" and had warned others about Giuliani as far back as March. He felt the shadow diplomacy was undermining decades of foreign policy and the rule of law in Ukraine and that was "wrong," said Rep. Gerry Connolly, D-Va.
Connolly said Kent described the results of a May 23 meeting at the White House, organized by Trump's acting chief of staff, Mick Mulvaney, where three administration officials — U.S. ambassador Gordon Sondland, special envoy Kurt Volker and Energy Secretary Rick Perry — declared themselves the people now responsible for Ukraine policy.
"They called themselves the three amigos," Connolly said Kent testified, and they said as much to Zelenskiy in Ukraine when they visited.
Kent also told them that Trump, through the Office of Management and Budget, which Mulvaney previously led, was holding up military aid to Ukraine while pressing Zelenskiy to investigate a company linked to Biden's son.
"He was clearly bothered by the role Mr. Giuliani was playing," Connolly said.
In 10 hours of testimony Monday, Hill, the former White House aide who was a top adviser on Russia, recalled to investigators that Bolton had told her he was not part of ``whatever drug deal Sondland and Mulvaney are cooking up,'' an apparent reference to talks over Ukraine.
She testified that Bolton asked her to take the concerns to National Security Council lawyer John Eisenberg.
As White House lawyers now try to learn more about the handling of the Ukraine call, Eisenberg is coming under particular scrutiny, said one White House official. He was both the official who ordered that the memorandum of the call be moved to a highly-classified system, and the one who involved the Justice Department in a complaint from the CIA general counsel. The latter caught the attention of the president, according to the official.
Giuliani said Tuesday he was "very disappointed" in Bolton's comment. Bolton, Giuliani said, ``has been called much worse.''
Giuliani also acknowledged he had received payments totaling $500,000 related to the work for a company operated by Lev Parnas — who, along with associate Igor Fruman, played a key role in Giuliani's efforts to launch a Ukrainian corruption investigation against Biden and his son Hunter. The two men were arrested last week on campaign finance charges as they tried to board an international flight.
Trump's team won't comply with the Democratic inquiry. Giuliani and Vice President Mike Pence became the latest officials refusing to cooperate, saying through their lawyers they would not provide information requested by House Democrats as part of the impeachment inquiry.
The chairman leading the impeachment investigation, Rep. Adam Schiff, D-Calif., said the stonewalling simply bolsters the charge that Trump is obstructing Congress.
"The case for Congress continues to build," Schiff said. He said Defense Secretary Mark Esper told investigators Sunday that he would comply with a subpoena request, only to be "countermanded" by a higher authority, likely Trump.
Sondland, whose text messages with other diplomats are part of a cache released by Volker and made public earlier this month, is scheduled to appear for an interview Thursday.
The interviews Monday and Tuesday, like the others conducted by House impeachment investigators, took place behind closed doors. Republican lawmakers have aimed their ire at the process, saying witnesses should be interviewed out in the open.
Senate Majority Leader Mitch McConnell said Democrats were trying to "cancel out" Trump's election with the march toward impeachment.
Five more officials are scheduled this week, mostly from the State Department, though it is unclear if they will all appear.
Michael McKinley, a former Pompeo aide who resigned last week, is set to testify Wednesday. McKinley, a career foreign service officer and Pompeo's de facto chief of staff, resigned Friday, ending a 37-year career.
Once Democrats have completed the probe and followed any other threads it produces, they will use their findings to help determine whether to vote on articles of impeachment.