“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.

Some members of the House Intelligence Committee have begun calling for Sondland to return for additional questioning to reconcile the two diplomats’ accounts.