President Joe Biden acknowledged again Tuesday night that he underperformed at last week’s debate while saying he “wasn’t very smart” for having traveled extensively in the weeks leading up to the event in Atlanta.

“I decided to travel around the world a couple of times … shortly before the debate,” Biden said at a campaign fundraiser in McLean, Virginia.

“I didn’t listen to my staff … and then I almost fell asleep onstage,” he quipped.

“It’s not an excuse but an explanation,” he added. Aides previously said Biden had a cold during the debate.

It wasn’t immediately clear to what extent Biden was joking about almost falling asleep. Cameras aren’t allowed into his fundraisers, and the media relies upon written pool reports. Biden has a track record of making frank or unexpected comments at fundraisers.

In apologizing for his lackluster performance, he also stressed that it was “critical” to defeat former President Donald Trump in November.

Biden last month went to France to commemorate the 80th anniversary of D-Day and then returned to the U.S. before he departed for the Group of Seven Summit in Italy. He then had a Los Angeles fundraiser and later spent several days at Camp David, Maryland preparing for the debate.

Biden continues to defend his ability to take on Trump after a debate performance punctuated by a raspy voice and rhetorical missteps that left many Democrats anxious.

Rep. Lloyd Doggett, D-Texas, on Tuesday became the first sitting Democrat in Congress to call on Biden to withdraw from the race.

At a campaign rally Friday, Biden first addressed his performance from the previous night.

“I know I’m not a young man,” Biden, 81, told supporters in Raleigh, North Carolina. “I don’t walk as easy as I used to. I don’t speak as smoothly as I used to. I don’t debate as well as I used to, but I know what I do know — I know how to tell the truth!”

Biden is the oldest president in American history. Trump, 78, is the second oldest.