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Donald J. Trump said he was “blindsided” when Paul D. Ryan, the House speaker, withheld an endorsement from him this week, saying that Mr. Ryan had called to congratulate him after he won the New York primary on April 19.

“I was blindsided a little bit, because he spoke to me three weeks ago, and it was a very nice call, a very encouraging call,” Mr. Trump told NBC’s “Meet the Press” in an interview that will air on Sunday. “I was doing well. He called me, I think, to congratulate me about New York, ’cause I won by massive numbers.”

But a spokesman for Mr. Ryan said Saturday that such a call never took place.

On Thursday, Mr. Ryan, a Republican from Wisconsin, told CNN that he was not ready to endorse the party’s presumptive nominee for president. Mr. Trump responded at the time with a statement saying he was not ready to support Mr. Ryan’s agenda.

On “Meet the Press,” Mr. Trump said of the purported phone call: “He called me to congratulate me. Couldn’t have been nicer.”

“I have a nice relationship with him,” he said. “Don’t know him well. Met him one time. But have a nice relationship with him. And then all of a sudden, he gets on and he does this number. So I’m not exactly sure what he has in mind. But that’s O.K.”

Brendan Buck, a spokesman for Mr. Ryan, said in an email: “They talked in March about our agenda but not since then.” A spokeswoman for Mr. Trump did not respond to an email asking for details.

The March phone call has also been a subject of dispute. Mr. Trump had said publicly that Mr. Ryan had called him. But Mr. Ryan, who had been critical of Mr. Trump’s more divisive comments, said he was responding to a request for a call by Mr. Trump.

Mr. Trump and Mr. Ryan are expected to meet in Washington on Thursday. In a separate interview with ABC’s “This Week,” Mr. Trump downplayed the need for party unity, in a major departure from how previous presumptive nominees have approached the post-primary process.

“I think it would be better if it were unified. I think it would be. There would be something good about it,” Mr. Trump said in the interview set to air on Sunday. “But I don’t think it actually has to be unified in the traditional sense.”