President Biden Says He Nearly 'Fell Asleep on Stage’ During Debate

President Biden is offering up an explanation for his lackluster performance debating Donald Trump ... he says his travel schedule had him running on fumes, and feeling sleepy.

Biden made the excuse Tuesday at a campaign fundraiser in McLean, Virginia ... and said he almost fell asleep on the debate stage.

POTUS blamed his lack of energy on being sapped from long trips in the weeks before Thursday's first presidential debate, including a trip to France in early June for the 80th anniversary of D-Day.

Biden told the room, "I decided to travel around the world a couple of times ... shortly before the debate ... I didn't listen to my staff ... and then I almost fell asleep on stage" ... according to pool reports from the fundraiser.

Remember ... Biden went to France the first week of June, flew to California for a big fundraiser in Los Angeles on June 15 and then spent a week preparing for the June 27 debate at Camp David.

Biden told supporters he was not providing an excuse but an explanation ... and went on to apologize for his debate performance while stressing the importance of beating Trump at the ballot box.

Worth noting ... the debate started at 9 PM and Axios national political correspondent Alex Thompson joined us Monday on "TMZ Live" and told us Biden is at his sharpest between 10 AM and 4 PM and is prone to mental mistakes later in the day.