Mr. Sondland testified on Wednesday that he had a conversation with the president on Sept. 9, and that an irritated Mr. Trump had told him he had never requested a “quid pro quo” from Mr. Zelensky.

But Mr. Trump’s comments ignored the bulk of the testimony offered by Mr. Sondland, who asserted that the president had expressly ordered him to work with his personal lawyer Rudolph W. Giuliani to dredge up unflattering information on his political rivals. Mr. Sondland also said the senior-most members of the administration were aware of the effort, including Vice President Mike Pence, Secretary of State Mike Pompeo and Mick Mulvaney, Mr. Trump’s acting chief of staff.

“Everyone was in the loop,” Mr. Sondland said. “It was no secret.”

The call between the president and Mr. Sondland — who was a high-dollar donor to Mr. Trump’s inauguration before embarking on a career in diplomacy — took place the same day the whistle-blower complaint that formed the basis for the impeachment inquiry was delivered to the House Intelligence Committee.

Mr. Sondland said Mr. Trump was “not in a good mood” that day.

“It was a very short abrupt conversation,” Mr. Sondland said about the September call. “He just said, ‘I want nothing, I want nothing, I want no quid pro quo.’”