House Democrats say testimony provided Tuesday by William B. Taylor Jr., the acting U.S. ambassador to Ukraine, could prove devastating to President Trump, showing he had his EU ambassador attempt to extort Ukraine using taxpayer money.

The testimony could pose a more immediate problem for that diplomat: Gordon Sondland. And his lawyer on Wednesday said his client either does not recall or disputes many of Taylor’s key accusations, The Washington Post reports.

Sworn testimony provided by Sondland, a hotelier and Trump fundraiser, and Taylor, a decorated veteran and career diplomat, now diverges on key points. Most critically, Taylor's testimony challenges Sondland's claim that he did not know of an alleged quid pro quo involving nearly $400 million in security aid for Ukraine. The White House held up the planned aid over the summer as Trump’s personal attorney Rudolph W. Giuliani worked with Sondland to press the former ­Soviet-bloc country to launch investigations that could help Trump politically.

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One of the probes Giuliani wanted involved a discredited theory that Ukraine tried to undermine Trump in the 2016 U.S. election. The other was about Burisma, a Ukrainian energy company that hired Hunter Biden when his father was vice president.

Sondland testified last week that he knew Giuliani had conditioned a coveted White House invite for Ukraine's new president, Volodymyr Zelensky, on such investigations. But he said he did not know whether the White House had also made security assistance contingent on Zelensky's committing to launch the probes.

Taylor, the senior U.S. diplomat in Ukraine, contradicted Sondland's account Tuesday. In prepared remarks delivered to congressional investigators, Taylor wrote that Sondland not only knew of such a quid pro quo, but also had communicated the threat to Ukraine.

Taylor said he understood that on Sept 1, Sondland warned Zelensky aide Andriy Yermak that the security assistance "would not come" unless Zelensky committed to pursuing the investigation into Burisma, which could have damaged Joe Biden, a top 2020 Democratic presidential hopeful.

"I was alarmed," Taylor wrote, saying a national security official had told him the demand was relayed in person by Sondland while the ambassador was traveling in Poland with Vice President Pence. "This was the first time I had heard that the security assistance . . . was conditioned on the investigation."

Responding to questions by email, Sondland's attorney Robert Luskin wrote to The Washington Post on Wednesday that his client "does not recall" such a conversation.

"Sondland does not recall any conversation in Warsaw concerning the aid cutoff, although he understood that the Ukrainians were, by then, certainly aware of the cutoff and raised the issue directly with Pence," Luskin wrote.