WASHINGTON — The House impeachment inquiry is exposing new details about unease in the State Department and White House about President Donald Trump’s actions toward Ukraine and those of his personal lawyer Rudy Giuliani.

One witness said it appeared “three amigos” tied to the White House had taken over foreign policy. Another quoted national security adviser John Bolton as calling Giuliani a “hand grenade” for his back-channel efforts to get Ukraine to investigate Trump’s Democratic rival Joe Biden and Biden’s son Hunter.

On Wednesday, a former aide to Secretary of State Mike Pompeo arrived to speak to the House impeachment panels behind closed doors. Michael McKinley, who resigned last week, is a career foreign service officer and was Pompeo’s de facto chief of staff.

He is expected to discuss concerns held by career State Department officials about the treatment of the U.S. ambassador to Ukraine, Marie Yovanovitch, and others who worked on the Ukraine portfolio, according to a person familiar with his testimony. A Latin America specialist, McKinley wasn’t directly involved in Ukraine policy, but as a senior adviser to Pompeo was generally aware of the situation, the person said.

Rep. Mark Meadows, R-N.C., told reporters outside the closed-door hearing that McKinley was complimentary about Pompeo’s role but did raise other issues.

“I think most of this is a concern by a colleague for an ambassador that he held in high regard,” said Meadows said, declining to provide more details of the closed session.

McKinley was expected to talk about demoralization in the ranks of career foreign service officers and what many have lamented as the politicization of the once-apolitical bureaucracy, according to the person, who was granted anonymity to speak about his remarks.

The 37-year veteran of the diplomatic corps was known to be unhappy with the state of affairs although his farewell note to colleagues mentioned nothing about the reason for his departure other than it was a “personal decision.”

Another key figure in the impeachment investigation, special envoy Kurt Volker, returned to Capitol Hill on Wednesday. He and his lawyer were to review the transcript of his Oct. 3 testimony to investigators, according to a person familiar with his appearance who was not authorized to discuss it. Republicans say all the transcripts from the investigation should be released to the public.

Volker provided text messages to lawmakers that revealed an effort at the State Department to push Ukraine’s leader into opening an investigation of the gas company Burisma, connected to Joe Biden’s son, in return for a visit with Trump.

That effort soon escalated into what one diplomat feared was a quid pro quo for U.S. military aid. Trump has denied that, saying assistance to Ukraine was delayed to pressure the country into addressing corruption.

The testimony so far 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.

Trump’s July 25 phone call in which he pressed Ukraine’s president to investigate the Bidens is at the center of the Democrats’ inquiry.

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.

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.

Trump and congressional leaders will be meeting later Wednesday at the White House on other matters.

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.

Rep. Adam Schiff, D-Calif., the chairman of the Intelligence Committee overseeing the probe, has praised the State Department officials for stepping forward, under subpoena, to shed light on the matter.

“We have learned much of this thanks to the courageous testimony of the State Department officials who have been put in an impossible situation by the administration,” which is urging them not to comply with requests to testify to Congress, he said. “They are doing their duty.”

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.

Kent was concerned about the “fake news smear” against 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 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.

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.