WASHINGTON — An ambassador at the center of the House impeachment inquiry testified on Wednesday that he was following President Trump’s orders with the full knowledge of several other top administration officials when he pressured the Ukrainians to conduct investigations into Mr. Trump’s political rivals, detailing what he called a clear quid pro quo directed by the president.
Gordon D. Sondland, a wealthy Republican megadonor appointed by Mr. Trump as the ambassador to the European Union, told the House Intelligence Committee that he reluctantly followed Mr. Trump’s directive to work with Rudolph W. Giuliani, the president’s personal lawyer, as he pressured Ukraine to publicly commit to investigating former Vice President Joseph R. Biden Jr. and an unsubstantiated theory that Democrats conspired with Kyiv to interfere in the 2016 election.
“We followed the president’s orders,” Mr. Sondland said.
In testimony that amounted to an act of defiance by an official who has been described by other witnesses as a point man in the push to extract the investigations, Mr. Sondland tied the most senior members of the administration to the effort — including the vice president, the secretary of state, the acting chief of staff and others. He said they were informed of it at key moments.
As striking as his account was, Mr. Sondland appeared on Wednesday as a highly problematic witness. He has had to revise his account several times based on testimony from others, repeatedly claimed not to have recalled key episodes and conceded before the committee that he did not take notes that could give him certainty about precisely what happened.
Still, the revelations he offered, along with emails corroborating them, were stunning.
Secretary of State Mike Pompeo signed off on parts of the pressure campaign, Mr. Sondland testified, and Mick Mulvaney, the acting White House chief of staff, was deeply involved. They understood, as he did, that there was a quid pro quo linking a White House meeting for President Volodymyr Zelensky of Ukraine to a promise by him to announce investigations into Mr. Trump’s political rivals, he said.
“I know that members of this committee have frequently framed these complicated issues in the form of a simple question: Was there a quid pro quo?” Mr. Sondland said. “As I testified previously, with regard to the requested White House call and White House meeting, the answer is yes.”
“Everyone was in the loop,” he said. “It was no secret.”
And Mr. Sondland testified that he came to believe that there was another linkage being made by Mr. Trump, between vital military assistance approved by Congress for Ukraine and a public commitment by its president to investigate Mr. Trump’s political adversaries. Mr. Sondland said he informed Vice President Mike Pence of his concern about that connection during a Sept. 1 meeting in Warsaw.
His appearance raised questions about whether the other top administration figures will come forward to testify in the inquiry and push back on Mr. Sondland’s version of events.
Almost two months after House Democrats began their impeachment inquiry, Mr. Sondland’s account came as close as investigators have gotten to an admission from an official who dealt directly with Mr. Trump. But it came with the blemishes of Mr. Sondland’s shifting accounts, which have evolved since the committee first deposed him in October, opening him up to criticism from Republicans who claimed he was unreliable and not credible.
The State Department sought to block Mr. Sondland from testifying, and refused to allow him access to certain documents, which it also withheld from the committee despite a subpoena. Without access to them, Mr. Sondland said, he simply could not fully reconstruct the particulars of the conversations and meetings lawmakers pressed him on.
Democrats pointed to the administration’s stonewalling as yet another piece of evidence for an impeachment article against Mr. Trump for obstruction of Congress. And they quickly seized on what Mr. Sondland did say as bombshells.
“It goes right to the heart of the issue of bribery, as well as other potential high crimes and misdemeanors,” Representative Adam B. Schiff, Democrat of California and the chairman of the Intelligence Committee, told reporters during a brief break in the hearing.
Republicans, moving to discredit Mr. Sondland, seized on his assertion that Mr. Trump never personally or explicitly told him about preconditions on the White House meeting or the security assistance being released.
“President Trump never told me directly that the aid was conditioned on the investigations,” Mr. Sondland said under questioning. “The aid was my own personal guess based, again, on your analogy, two plus two equals four.”
Representative Michael R. Turner, Republican of Ohio, hammered on the point, his voice rising as he sharply questioned the ambassador.
“No one told you? Not just the president — Giuliani didn’t tell you, Mulvaney didn’t tell you, nobody?” Mr. Turner said. “Pompeo didn’t tell you?
“No one on this planet told you that President Trump was tying aid to investigations,” he added. “Yes or no?”
“Yes,” Mr. Sondland responded.
The ambassador, who smiled often during his appearance in the stately committee room and cheerfully admitted to a flair for colorful language and frequent use of “four-letter words” in his conversations with Mr. Trump, appeared to relish pulling other top officials into the spotlight with him after weeks of being cast by Republicans as a rogue actor. If he was uneasy about wreaking havoc on the defense of a president for whom he still works, Mr. Sondland did not show it.
“The suggestion that we were engaged in some irregular or rogue diplomacy is absolutely false,” he said, pointing to messages and phone calls in which he kept the White House and the State Department informed of his actions. “Any claim that I somehow muscled my way into the Ukraine relationship is simply false.”
Mr. Sondland’s appearance was the centerpiece of a crammed week of testimony before the Intelligence Committee. On Wednesday evening, two more officials — Laura K. Cooper of the Defense Department and David Hale of the State Department — were expected to deliver accounts related to the suspension of the security aid for Ukraine.
It could create new legal and political pressure on senior officials who either have refused to testify in the inquiry or have not yet been called, including Mr. Pompeo, Mr. Mulvaney and John R. Bolton, the president’s former national security adviser.
Standing on the South Lawn of the White House while Mr. Sondland was still at the witness table, Mr. Trump tried to distance himself from the ambassador.
“I don’t know him very well — I have not spoken to him much,” Mr. Trump told reporters before departing on a trip to Texas.
“Easy come, easy go” Mr. Sondland said with a smile, when a lawmaker asked him about the presidential brushoff.
Holding a page of notes scrawled in marker in large block letters, Mr. Trump read aloud from a section of Mr. Sondland’s closed-door deposition in which the ambassador described a phone call in which the president had told him he did not want a quid pro quo.
“This is the final word from the president of the United States,” Mr. Trump said, shouting to be heard over the hum of helicopter rotors. “‘I want nothing.’”
That conversation occurred after the White House was aware that a whistle-blower had filed a complaint alleging that Mr. Trump was abusing his power to try to enlist Ukraine to help him in the 2020 presidential election.
Through an aide, Mr. Pence denied that the two men had spoken as Mr. Sondland recounted.
“Ambassador Gordon Sondland was never alone with Vice President Pence on the Sept. 1 trip to Poland,” Marc Short, his chief of staff, said in a statement. “This alleged discussion recalled by Ambassador Sondland never happened.”
Mr. Pompeo pushed back as well, although a statement from his spokeswoman did not directly address Mr. Sondland’s assertion that the secretary of state knew and approved of his efforts to get Ukraine to announce the investigations.
“Gordon Sondland never told Secretary Pompeo that he believed the president was linking aid to investigations of political opponents,” Morgan Ortagus, the State Department spokeswoman, said in the statement.
At times, representatives of both parties grew frustrated with Mr. Sondland, but Republicans were particularly eager to paint Mr. Sondland as unreliable.
“You don’t have records,” said Steve Castor, Republicans’ staff lawyer. “You don’t have your notes because you didn’t take notes. You don’t have a lot of recollections. I mean, this is like the trifecta of unreliability.”
Still, on matters at the heart of the inquiry, Mr. Sondland’s account was singularly damning. He confirmed the contents of a July 26 phone call he had with Mr. Trump, in which they discussed the need for the Ukrainian officials to announce the investigations Mr. Trump wanted.
He said that he, Energy Secretary Rick Perry and Kurt D. Volker, the special envoy for Ukraine, grudgingly worked with Mr. Giuliani on a pressure campaign “at the express direction of the president of the United States.”
“Simply put, we played the hand we were dealt,” Mr. Sondland said. “We all understood that if we refused to work with Mr. Giuliani, we would lose an important opportunity to cement relations between the United States and Ukraine. So we followed the president’s orders.”
At another point, explaining how he came to understand that the United States relationship with Ukraine was contingent on the announcement of the investigations, Mr. Sondland said that “Mr. Giuliani was expressing the desires of the president of the United States, and we knew that these investigations were important to the president.”
Mr. Giuliani defied a subpoena from the House for written records in his possession related to his work in Ukraine, but Democrats never called him to testify because they did not want to give him a platform he would surely use to defend Mr. Trump and malign Mr. Biden and his son Hunter, who served on the board of a Ukrainian energy company while his father was vice president.
Federal prosecutors in Manhattan are investigating whether Mr. Giuliani broke lobbying laws in his dealings with Ukraine. They are scrutinizing Mr. Giuliani’s role in the recall of the American ambassador to Ukraine, Marie L. Yovanovitch, as part of a broader campaign Mr. Giuliani waged to pressure the Ukranians.
Defying the State Department’s wishes, Mr. Sondland shared previously unseen emails and texts that demonstrated how he kept Mr. Pompeo and other administration officials apprised of his efforts to push the Ukranians. They showed that Mr. Sondland told Mr. Pompeo about a statement the Ukranians were considering putting out that would commit them to the investigations, and a plan to have Mr. Zelensky speak directly with Mr. Trump about the matter.
“The contents will hopefully make the boss happy enough to authorize an invitation,” Mr. Sondland wrote in an email to Mr. Pompeo.
A week and a half later, Mr. Sondland sent Mr. Pompeo another email asking whether he should arrange a meeting in Warsaw for Mr. Trump where Mr. Zelensky would “look him in the eye” and promise him the investigations, to break the “logjam” in relations between the two countries.
“Yes,” Mr. Pompeo responded in an emailed response. The meeting never materialized.
Another email showed that Mr. Sondland told Mr. Pompeo, Mr. Mulvaney and other top aides that Mr. Zelensky was likely to commit to the investigations when he and Mr. Trump spoke by phone in July.
Mr. Mulvaney had responded by saying he had asked the National Security Council to set up the call for the next day.
Mr. Sondland even took shots at Mr. Bolton, who other witnesses have said harbored deep concerns over the ambassador’s actions and repeatedly instructed subordinates to report them to White House lawyers.
“Before his visit to Kyiv, Ambassador Bolton’s office requested Mr. Giuliani’s contact information,” said Mr. Sondland, who repeated himself and then paused to smirk before continuing with his testimony.
Emily Cochrane contributed reporting.