Rudolph W. Giuliani, President Trump’s lead personal lawyer, said on Sunday that the president never had a conversation last year with James B. Comey, then the F.B.I. director, about ending the investigation into the fired national security adviser Michael T. Flynn, contradicting a memo Mr. Comey wrote at the time.

Mr. Giuliani’s statement, made during an appearance on CNN’s “State of the Union,” also appeared at odds with his own previous comments. While the White House has previously denied that Mr. Trump had asked Mr. Comey to drop the investigation, Mr. Giuliani had suggested that the two had discussed the inquiry, but in a way different from Mr. Comey’s account.

“There was no conversation about Michael Flynn,” Mr. Giuliani said Sunday. “The president didn’t find out that Comey believed there was until about — I think it was February when it supposedly took place. Memo came out in May.”

He continued: “And in between, Comey testified under oath that in no way had he been obstructed at any time. And then, all of a sudden, in May, he says he felt obstructed, he felt pressured by that comment, ‘You should go easy on Flynn.’ So we — we maintain the president didn’t say that.”