WASHINGTON — Ambassador Gordon Sondland told House impeachment investigators today that he worked with Rudy Giuliani on Ukraine at the “express direction” of President Donald Trump and pushed for a political “quid pro quo” with Kyiv because it was what Trump wanted.

“Mr. Giuliani was expressing the desires of the president of the United States, and we knew that these investigations were important to the president,” Sondland testified of his dealings with Trump’s personal attorney.

Sondland, the most highly anticipated witness in the public impeachment probe, made clear that he believed Trump was pursuing his desire for political investigations in return for an Oval Office meeting that the Eastern European nation’s new president sought to bolster his alliance with the West. Sondland said he later came to believe military aid that Ukraine relied on to counter Russia was also being held up until the investigations were launched.

In a blockbuster morning of testimony, Sondland’s opening remarks included several key details: He confirmed that he spoke with Trump on a cellphone from a busy Kyiv restaurant the day after the president prodded Ukraine’s leader to investigate political rival Joe Biden.

He also said he kept Secretary of State Mike Pompeo and other top administration officials aware of his dealings with Ukraine on the investigations Trump sought. Sondland said he specifically told Vice President Mike Pence he “had concerns” that U.S. military aid to Ukraine “had become tied” to the investigations.

“Everyone was in the loop,” Sondland testified in opening remarks. “It was no secret.”

Trump, speaking to reporters outside the White House today, said he does not know Sondland well.

Addressing the idea of trading access or aid for investigations, he said, speaking from notes written with a black marker, “I want nothing.” He said he never wanted any quid pro quo.

And a top Pence aide quickly denied that the brief conversation Sondland described between himself and the vice president had occurred. It “never happened,” said Pence chief of staff Marc Short.

Sondland said that conditions on any potential Ukraine meeting at the White House started as “generic” but “more specific items got added to the menu including — Burisma and 2016 election meddling.” Burisma is the Ukrainian gas company where Joe Biden’s son Hunter served on the board of directors. And, he added, “the server,” the hacked Democratic computer system.

“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?’ As I testified previously, with regard to the requested White House call and White House meeting, the answer is yes,” he said.

Sondland said he didn’t know at the time that Burisma was linked to the Bidens but has since come to understand that – and that the military aid also hinged on the investigations.

“President Trump never told me directly that the aid was conditioned on meetings,” he testified. “The only thing we got directly from Giuliani was that the Burisma and 2016 elections were conditioned on the White House meeting. … The aid was my own personal guess … two plus two equals four.”

The impeachment inquiry focuses significantly on allegations that Trump sought investigations of Democrat Joe Biden and his son — and the discredited idea that Ukraine rather than Russia interfered in the 2016 U.S. election — in return for the badly needed military aid for Ukraine and the White House visit.

Sondland, a wealthy hotelier and Trump donor, has emerged as a central figure in an intense week in the impeachment prone that has featured nine witnesses testifying over three days. Both Democrats and Republicans were uncertain about what Sondland would testify to, given that he had already clarified parts of his initial private deposition before lawmakers.

Sondland appeared prepared to fend off scrutiny over the way his testimony has shifted in closed-door settings, saying “my memory has not been perfect.” He said the State Department left him without access to emails, call records and other documents he needed in the inquiry.

Still, he did produce new emails and text messages to bolster his assertion that others in the administration were aware of the investigations he was pursuing for Trump from Ukraine.

Sondland insisted, twice, that he was “adamantly opposed to any suspension of aid” for Ukraine. “I was acting in good faith. As a presidential appointee, I followed the directions of the president.”

The son of immigrants who he said escaped Europe during the Holocaust, Sondland described himself as a “lifelong Republican” who has worked with officials from both parties, including Biden.

Dubbed one of the “three amigos” pursuing Ukraine policy, Sondland is disputing that they were running some “rogue ” operation outside official U.S. policy. He produced emails and texts showing he, former special envoy Kurt Volker and Energy Secretary Rick Perry kept Pompeo and others apprised of their activity. One message from Volker said, “Spoke w Rudy per guidance from S.” He said, “S means the secretary of state.”

He said the State Department “was aware that a commitment to investigations was among the issues we were pursuing.”

Democratic Intelligence Committee Chairman Adam Schiff of California opened the hearing saying, “The knowledge of this scheme was far and wide.”

Schiff warned Pompeo and other administration officials who are refusing to turn over documents and testimony to the committee “they do so at their own peril.” He said obstruction of Congress was included in articles of impeachment during Watergate.

The top Republican on the committee, Devin Nunes of California, decried the inquiry and told the ambassador, “Mr. Sondland, you are here to be smeared.”

Nunes renewed his demand to hear from the still-anonymous whistleblower whose complaint about Trump’s July 25 phone call with Ukraine President Volodymyr Zelenskiy led the House to open the impeachment inquiry.

Associated Press writer Colleen Long, Laurie Kellman and Zeke Miller in Washington contributed to this report.