WASHINGTON — U.S. Ambassador to the European Union Gordon Sondland made a significant change to his testimony to House impeachment investigators this week: He said he now remembers telling a top aide to Ukrainian President Volodymyr Zelenskiy that Ukraine would not receive U.S. military assistance until it committed to investigating the 2016 election and former Vice President Joe Biden.

Sondland's latest testimony — stated in a three-page declaration to the House committees leading the impeachment inquiry into President Donald Trump — represents an update to the testimony he gave in October and contains significant new details. That includes a fuller accounting of the role he played in personally telling the Ukrainians they needed to cooperate with the demands of Trump's personal attorney, Rudy Giuliani, if they wanted the aid money.

The timeline of events Sondland first outlined in his opening statement in October largely absolved him of any wrongdoing or of having any advance knowledge of a scheme to use U.S. foreign policy to promote Trump’s political interests. That characterization, however, was at stark odds with both the testimony of other officials and with written records obtained by the House in its impeachment inquiry. His new testimony makes clear that he had been well aware that releasing foreign aid was conditional to Ukraine launching the desired investigations.

According to the new sworn declaration, Sondland told Congress that his memory was "refreshed" after reviewing the opening statements given to Congress by Bill Taylor, the acting ambassador to Ukraine, and Tim Morrison, a former adviser to Trump on Russian and European affairs.

Morrison told investigators that a conversation he had with Sondland gave him reason to believe that the release of aid to Ukraine might be tied to the country making a public anti-corruption statement that would announce the revival of an investigation into the energy company Burisma Holdings, the Ukrainian gas company whose board of directors Biden’s son Hunter Biden joined in 2014.

Taylor testified behind closed doors that Sondland had told him of an effort by the president to link security aid for Ukraine to probes of the Bidens and matters related to the 2016 presidential election.

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Sondland said that by the beginning of September, he “presumed that the aid suspension had become linked to the proposed anti-corruption statement.”

Sondland said he also now remembered a Sept. 1 conversation in Warsaw with Andriy Yermak, a top Zelenskiy adviser, in which he told Yermak that "the resumption of U.S. aid would likely not occur until Ukraine provided the public anti-corruption statement that we had been discussing for many weeks."

He also said that soon after, he "came to understand" the statement would have to come from Zelenskiy himself. He claimed he doesn't remember exactly how he learned this, but that he thought it may have come from Giuliani or Kurt Volker, then-U.S. special envoy to Ukraine who resigned after his name appeared in a whistleblower complaint about Trump’s dealings with Ukraine.

Sondland previously told Congress that the idea for Zelenskiy to deliver a public statement later “morphed” into “some kind of an interview that President Zelenskiy would give to a TV station.”

Asked with what network, Sondland said, “I don't know, but something President Trump would see.”

“Tucker,” he added, referring to Fox News host Tucker Carlson’s weeknight program.

The release of Sondland’s latest round of testimony came at the same time as the committees also released a transcript of his prior testimony in October as well as of Volker’s testimony from October.

In addition, a fresh round of text messages given to the committee by Volker and released Tuesday revealed specifics about the language of the public anti-corruption statement that had been drafted for Zelenskiy to read.

According to the texts, Yermak sent Volker a draft that did not include specific mention of Burisma or the 2016 election on August 11. But Volker asked Yermak to add “the 2 key items” to it, and the next draft included specific mentions of “Burisma” and the “2016 U.S. elections.”

The transcript of Sondland's October testimony, however, paints a picture of a diplomat deeply entrenched in unorthodox channels who nonetheless found the push by the White House to launch politically advantageous investigations increasingly "insidious."

In that transcript, Sondland called the saga "sort of a continuum" that "started as talk to Rudy, then others talk to Rudy."

"Corruption was mentioned. Then, as time went on — and, again, I can’t nail down the dates — then let’s get the Ukrainians to give a statement about corruption. And then, no, corruption isn’t enough, we need to talk about the 2016 election and the Burisma investigations. And it was always described to me as ongoing investigations that had been stopped by the previous administration and they wanted them started up again. That’s how it was always described. And then finally at some point I made the Biden-Burisma connection, and then the transcript was released," Sondland said.

"It kept getting more insidious as [the] timeline went on, and back in July, it was all about just corruption," Sondland added, according to the transcript.

There is no evidence of wrongdoing by either Biden.

Sondland also said in his original deposition that he grew frustrated with how conditions were continually being added for Ukraine to get a meeting with Trump.

"We were jerking Ukraine around, and I didn’t like it," Sondland said, according to the transcript.

Later, in the the transcript, Sondland suggests that he understood efforts to have the Ukrainians investigate the Bidens were unlawful.

When asked if he felt the efforts were “illegal,” he responded, “I’m not a lawyer, but I assume so.”

Trump has repeatedly denied engaging in a quid pro quo with Ukraine. In a statement, the White House said the transcripts released Tuesday "show there is even less evidence for this illegitimate impeachment sham than previously thought."

White House press secretary Stephanie Grisham said that Sondland "squarely states that he 'did not know, (and still does not know) when, why or by whom the aid was suspended' and that he said he 'presumed' there was a link to the aid — but cannot identify any solid source for that assumption."

"No amount of salacious media-biased headlines, which are clearly designed to influence the narrative, change the fact that the President has done nothing wrong," Grisham said.

According to the transcript of his October testimony, Sondland revealed that Trump had seized on a baseless conspiracy theory — known in some circles as "the insurance policy" — that the Democratic National Committee framed Russia for election interference in 2016 and that Ukraine had attempted to help Hillary Clinton win.

"'They tried to take me down,'" Sondland quotes Trump as saying, referring to Ukraine and the DNC. "He kept saying that over and over."

In a statement, the chairs of the three committees leading the inquiry — House Intelligence Committee Chair Adam Schiff, D-N.Y., House Foreign Affairs Committee Chair Eliot Engel, D-N.Y. and House Oversight Committee acting Chair Carolyn Maloney, D-N.Y. — said the testimony of Sondland and Volker “shows the progression of efforts by the president and his agent, Rudy Giuliani, to use the State Department to press Ukraine to announce investigations beneficial to the president’s personal and political interests.”

A key figure in the unfolding impeachment inquiry, Sondland had no diplomatic experience before Trump nominated him in 2017 to become ambassador to the E.U., a club of nations that does not include Ukraine. He was a wealthy hotelier who donated about $1 million to Trump’s inaugural committee and refers to himself in his prepared testimony as a “lifelong Republican.”

His depiction of a Trump-ordered campaign to pressure Zelenskiy to open an investigation adds to a growing body of testimony corroborating the underlying allegations contained in a whistleblower’s complaint that led the House to launch the impeachment inquiry late last month. Trump has maintained he did "nothing wrong" and that all his efforts on Ukraine were both legal and appropriate.

At points in his testimony, Sondland had problems recalling key events described by other witnesses.

Asked about a July 10 meeting with White House and Ukrainian officials where Sondland allegedly said he’d worked out a deal with acting White House chief of staff Mick Mulvaney that Zelenskiy could have a meeting with the president if Ukraine opened “investigations,” Sondland said he couldn’t remember.

Sondland also testified in his original deposition that he didn't remember whether he told Marie Yovanovitch, the ousted U.S. ambassador to Ukraine, that she should tweet out support or praise for Trump if she wanted to save her job, as she told House impeachment investigators, according to a transcript of her testimony released on Monday.

Josh Lederman reported from Washington, and Adam Edelman from New York.