WASHINGTON — U.S. Ambassador to the European Union Gordon Sondland told House impeachment investigators this week that 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, according to a person with knowledge of Sondland’s testimony.

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.

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.

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 with Andriy Yermak, a top Zelenskiy adviser, in Warsaw 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 that he “came to understand” the statement would have to come from Zelenskiy himself. He claims he doesn’t remember how he learned that but it may have come from Trump’s personal lawyer Rudy 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.

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.

The transcript of Sondland’s October testimony 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, a reference to the Ukrainian gas company Burisma Holdings, whose board of directors Biden’s son Hunter Biden joined in 2014.

“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.

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 — 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.”

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