Acting White House chief of staff Mick Mulvaney said at a news conference Thursday that President Trump withheld nearly $400 million in military aid in part to pressure Ukraine to pursue an investigation that could benefit him politically — acknowledging before the nation a quid pro quo that is at the heart of an impeachment inquiry and that the president and his allies have vigorously denied for weeks.

Mulvaney told reporters that Trump wanted the government in Kyiv to investigate a debunked conspiracy theory that a hacked Democratic National Committee computer server was taken to Ukraine in 2016 to hide evidence that it was that country, not Russia, that interfered in the presidential election.

“Did [Trump] also mention to me in the past the corruption related to the DNC server?” he said. “Absolutely, no question about that. But that’s it, and that’s why we held up the money.”

Mulvaney denied that the aid was also contingent on a Ukrainian investigation of former vice president Joe Biden, or Biden’s son Hunter, another potential quid pro quo that congressional Democrats are looking into as part of the impeachment inquiry.

Mulvaney defended the president’s actions as commonplace and appropriate. “I have news for everybody: Get over it. There’s going to be political influence in foreign policy,” Mulvaney said.

Later, after Trump’s lawyer and other Republicans distanced themselves from Mulvaney, the White House scrambled to walk back his comments, issuing an official statement blaming the media for misconstruing his words “to advance a biased and political witch hunt against President Trump.”

“Let me be clear,” Mulvaney’s written statement said, “there was absolutely no quid pro quo between Ukrainian military aid and any investigation into the 2016 election. There was never any connection between the funds and the Ukrainians doing anything with the server . . . there was never any condition on the flow of the aid related to the matter of the DNC server.”

Mulvaney’s comments at the news conference — and his attempt to back out of them — added to a growing swirl of crisis around Trump, brought on not only by the specter of impeachment but also his erratic decision-making regarding the country’s military presence in Syria and the announcement Thursday, also by Mulvaney, that next year’s G-7 summit of world leaders will be held at Trump’s Miami resort. That decision, which could enrich the president while raising the profile of one of his struggling properties, has been widely criticized as an unprecedented conflict of interest.

On Capitol Hill, where Democrats are building their case against the president, impeachment investigators spent nine hours Thursday deposing U.S. Ambassador to the European Union Gordon Sondland, the latest in a succession of officials to appear for closed-door testimony about the administration’s dealings with Ukraine.

Sondland told them that the president had outsourced U.S. policy on Ukraine to Trump’s personal attorney Rudolph W. Giuliani — a decision he said he disagreed with but carried out nonetheless. Giuliani had been pushing the Ukrainians to investigate interference in the 2016 election.

In a sign of how potentially damaging Mulvaney’s remarks were, Jay Sekulow, another of Trump’s personal attorneys, released a statement that said: “The President’s legal counsel was not involved in acting chief of staff Mick Mulvaney’s press briefing.” Within the hour, Mulvaney issued his statement attempting to walk back what he’d said earlier.

Even before Sekulow issued his statement, a Justice Department official took issue with Mulvaney’s original remarks: “If the White House was withholding aid in regards to the cooperation of any investigation at the Department of Justice, that is news to us.”

Mulvaney’s comments alarmed and incensed some Republicans, who have supported Trump but were unaware whether the White House was intentionally shifting its defense strategy.

“Totally inexplicable,” said one GOP lawmaker, speaking on the condition of anonymity to be candid. “He literally said the thing the president and everyone else said did not happen.”

To the Democrats on the three panels conducting the impeachment probe, Mulvaney’s words marked a significant turning point.

“We have a confession from the president,” said Rep. Eric Swalwell (D-Calif.), a member of the House Intelligence Committee, referring to Trump’s July 25 phone call with Ukrainian President Volodymyr Zelensky, during which Trump pressured his counterpart to open investigations into the 2016 election and the Bidens.

Mulvaney, Swalwell said, “co-signed the president’s confession,” adding that the administration was still engaging in “an ongoing coverup.”

During his news conference, Mulvaney denied such assertions, saying the administration had not attempted to hide anything by moving a transcript of Trump’s phone call with Zelensky to a more secure server at the White House.

“Let me ask you this: If we wanted to cover this up, would we have called the Department of Justice almost immediately and have them look at the transcript of the tape, which we did, by the way?” Mulvaney said. “If we wanted to cover this up, would we have released it to the public?”

As Mulvaney jousted with reporters at the White House, members of the House Intelligence, Oversight and Foreign Affairs committees — which are conducting the impeachment probe — questioned Sondland, who said he was uncomfortable with the decision to cede responsibility for Ukraine policy to Giuliani. “I would not have recommended that Mr. Giuliani or any private citizen be involved in these foreign policy matters,” Sondland said, according to his prepared remarks.

Mulvaney dismissed those concerns, defending the president’s right to put foreign policy in the hands of his personal lawyer.

“You may not like the fact that Giuliani was involved. That’s great; that’s fine,” Mulvaney said, referencing Sondland’s remarks. “It’s not illegal. It’s not impeachable . . . The president gets to set foreign policy, and he gets to choose who to do so, as long as it doesn’t violate any law.”

Sondland, a major Trump donor who has become a focus of the impeachment inquiry because of his outsize role in U.S.-Ukraine policy, criticized the president’s temporary hold on aid and the recall of the former U.S. ambassador to Ukraine, Marie Yovanovitch. Sondland called her an “excellent diplomat” and said he “regretted” her departure, which followed a campaign by Giuliani to paint her as disloyal to the president.

Democratic lawmakers emerging from Sondland’s deposition said that although they found him to be generally credible and were glad that he chose to testify despite White House pressure not to, they thought Sondland was being selective and cagey with details.

“I think he’s clearly trying to defend his reputation and his own behavior,” said Rep. David N. Cicilline (D-R.I.), a member of the Foreign Affairs Committee. He also criticized some of Sondland’s testimony as “not credible to me, with respect to his sort of not understanding all the things that were happening around him, and in full view of the American people.”

In his prepared remarks, Sondland, a hotel magnate who came to the job with no diplomatic experience, depicts himself as a well-meaning but in some cases out-of-the-loop emissary for the president who tried to do what he could to prop up the government of Ukraine as it fends off Russian-backed separatists.

“I did not understand, until much later, that Mr. Giuliani’s agenda might have also included an effort to prompt the Ukrainians to investigate Vice President Biden or his son or to involve Ukrainians, directly or indirectly, in the President’s 2020 reelection campaign,” he said, explaining that he understood that Burisma, the Ukrainian energy firm that employed Hunter Biden, was “one of many examples of Ukrainian companies run by oligarchs and lacking the type of corporate governance structures found in Western companies.”

Sondland’s apparent failure to connect the dots between Burisma and the Bidens occurred as Giuliani made several televised appearances over the spring and summer criticizing Hunter Biden’s involvement on the board, and numerous newspaper and magazine articles questioned whether his role at Burisma could prove to be a drag on his father’s presidential campaign.

“Withholding foreign aid to pressure a foreign government to take such steps would be wrong,” he stated in his prepared testimony. “I did not and would not ever participate in such undertakings.”

But that testimony appears to conflict with what other current and former Trump administration officials told House investigators over the past two weeks.

Fiona Hill, the National Security Council’s former senior director for Russia and Europe, told House investigators that she was concerned by Sondland’s talk of investigations in a July meeting, which she eventually relayed to a lawyer for the National Security Council.

Deputy Assistant Secretary of State for Europe and Eurasia George Kent testified that Sondland was deputized, along with former special U.S. envoy to Ukraine Kurt Volker and Energy Secretary Rick Perry, to be one of “three amigos” running Ukraine policy. The move came during a May meeting that Mulvaney organized following Yovanovitch’s ouster.

Last week, Volker provided impeachment investigators with text messages showing that Sondland had said Trump, before agreeing to meet in person with his Ukrainian counterpart, wanted the “deliverable” of a promise from Zelensky to investigate Burisma and the 2016 election.

Sondland claimed that his pursuit of investigations in Ukraine were always in line with long-standing U.S. policy to push for transparency and anti-corruption efforts in the country. He added that he was never aware of objections to the plans for Ukraine policy from Hill or her boss, then-national security adviser John Bolton. Hill testified Monday that Bolton was livid that Giuliani was directing a shadow Ukraine policy.

“I have to view her testimony — if the media reports are accurate — as the product of hindsight and in the context of the widely known tensions between the NSC, on the one hand, and the State Department, on the other hand,” Sondland said.

Josh Dawsey, Matt Zapotosky and Carol D. Leonnig contributed to this report.