US president Joe Biden has blamed his poor performance at a TV debate with Donald Trump on jet lag.

During a campaign event, the 81-year-old Mr Biden pointed to two back-to-back European trips, saying: “I wasn’t very smart. I decided to travel around the world a couple of times.”

The president added that he “didn’t listen to my staff” about travel and joked that he “fell asleep on stage” during the debate.

However, Democratic leaders were increasingly signalling that they were not buying White House attempts to brush off Mr Biden’s performance in the face-off as a momentary lapse, after he gave halting and nonsensical answers and trailed off at times.

It comes as the president is set to meet with congressional leaders and Democratic governors, sit for a network TV interview and hold a press conference in the coming days, a blitz designed to push back against growing pressure for him to step aside from the 2024 race after the disastrous performance.

“We really want to turn the page on this,” White House press secretary Karine Jean-Pierre said of the intensifying calls for Mr Biden to bow out of the race.

She added that the president had no intention of stepping aside, characterising his debate failings as simply evidence of “a bad night” when he had a cold.

There is growing anxiety among donors and on Capitol Hill about the president’s ability to win come November. It is not helping that Mr Biden has yet to reach out to legislators, who are growing increasingly frustrated that the White House has not satisfactorily explained how such a seasoned politician could have performed so badly.

Questions swirled about whether this was an isolated incident or part of a pattern. Two people who spent time with Mr Biden behind closed doors described him similarly. He was often very sharp and focused, but he also had moments, particularly later in the evening, when his thoughts seemed jumbled and he would trail off mid-sentence or seem confused.

Former House Speaker Nancy Pelosi told MSNBC that she believes “it is a legitimate question” whether Mr Biden’s performance was just “an episode or is this a condition”.

“When people ask that question, it’s legitimate — of both candidates,” Mrs Pelosi said.

But she did not go so far as to ask him to step aside.

Mrs Pelosi said she had not spoken with Mr Biden since the debate, but she emphasised that the president is on “top of his game, in terms of knowing the issues and what is at stake”.

A spokesman later said Mrs Pelosi had full confidence in Mr Biden and “looks forward to attending his inauguration on January 20, 2025”.

Mr Biden has acknowledged that he had performed poorly, telling supporters he was not as young as he once was, but that he knew how to deliver doing the job.But allies worry that the next inevitable misstep by Biden — even if it’s not at the magnitude of his debate disaster — will resurrect voter concerns about the president’s fitness for office.