President Joe Biden attributed his poor debate performance last week to jet lag, telling reporters he “wasn’t very smart” for “travelling around the world a couple of times” before the debate. “I didn’t listen to my staff… and then I nearly fell asleep on stage,” he admitted.

Mr. Biden, 81, last returned from travel on June 15, nearly two weeks before the June 27 debate. His remarks come amid growing concerns within his party about his mental fitness ahead of November’s election. This follows a call from Texas Congressman Lloyd Doggett, the first sitting Democratic lawmaker, urging Biden to step aside after the debate. “I am hopeful that he will make the painful and difficult decision to withdraw,” Rep. Doggett said in a statement on Tuesday.

During the debate with former President Donald Trump last Thursday, Biden appeared to struggle with some responses. At a private fundraiser in Virginia on Tuesday evening, he said, “It’s not an excuse but an explanation,” referring to his travel. He also apologized for his performance and emphasized the importance of winning re-election, according to ABC News.

Mr. Biden made two separate trips to Europe within two weeks last month.

On June 15, President Joe Biden appeared at a fundraiser alongside former President Barack Obama after an overnight trip from Italy, returning to Washington DC the following day. White House officials have previously stated that he was battling a cold on the day of the debate.

However, the president did not mention any illness in his remarks on Tuesday. A White House spokeswoman confirmed earlier that he was not taking any cold medication during the debate.

Biden also spent six days at Camp David, the presidential retreat outside Washington DC, preparing for his debate against Donald Trump. According to The New York Times, which cited an unnamed source familiar with Biden’s schedule, his days at Camp David began at 11:00 each morning, and he was allotted time each day to nap.