Mr. Trump has given differing accounts of his contacts last year with Russians. He told The Times in March that he never met with Russians on behalf of the campaign, a statement his lawyer has since said was meant to refer to Russian government officials. In July, he described the Trump Tower meeting as primarily focused on the issue of Russian adoptions, before eventually acknowledging that he took the meeting because he was told Ms. Veselnitskaya had damaging information about Mrs. Clinton.

But intentionally misspeaking to Congress is a crime, giving his statement on Thursday added weight. If there were any doubt about the stakes, the office of Senator Chris Coons, Democrat of Delaware and a member of the panel, made them clear in an email to reporters on Thursday afternoon that included the text of the so-called False Statements statute.

Mr. Trump told investigators that working for his father’s campaign consumed his life. “I had never worked on a campaign before, and it was an exhausting, all-encompassing, life-changing experience. Every single day I fielded dozens, if not hundreds, of emails and phone calls.”

He is the second person connected to the Trump campaign to tell congressional investigators that the campaign was, essentially, too inexperienced and too unfamiliar with politics to pull off a master strategy — let alone coordinate with the Russian government. Mr. Trump’s brother-in-law, Jared Kushner, painted a similar picture during an interview with the Senate Intelligence Committee.

In his statement, Mr. Trump said he had some reservations about the June 2016 proposal from the meeting’s facilitator, Rob Goldstone, whom he described as a “colorful” music promoter he had come to know through the son of a Russian oligarch. Mr. Goldstone asked Mr. Trump to take a meeting that would include potentially damaging information about Mrs. Clinton.

“Since I had no additional information to validate what Rob was saying, I did not quite know what to make of his email,” he said. “I had no way to gauge the reliability, credibility or accuracy of any of the things he was saying.”

“As it later turned out, my skepticism was justified,” Mr. Trump added. “The meeting provided no meaningful information and turned out not to be about what had been represented.”