U.S. President Joe Biden told Democratic governors during a meeting at the White House on Wednesday that part of his plan going forward is to stop scheduling events after 8 p.m. so that he can get more sleep, according to three sources briefed on his comments.

The remarks, first reported by , came as the 81-year-old Biden sought to reassure a group of more than 20 state leaders about his ability to defeat former President Donald Trump in November and govern effectively for another four years.

Biden鈥檚 comment left several of the governors in the room frustrated, sources told CNN, and is one of the reasons that some of the participants have been rankled by the statement of loyalty and enthusiasm from them distributed by the Biden campaign on Thursday.

The White House did not immediately comment about what the president said. A Biden campaign aide argued that, as well as doing debate prep in the week after his two trips to Europe, Biden was engaged in hours of official work in addition to the hours of campaign work.

Biden also made a joke to the governors that didn鈥檛 go over well: 鈥淚鈥檓 fine 鈥 I don鈥檛 know about my brain, though.鈥 Jen O鈥橫alley Dillon, Biden鈥檚 campaign chairwoman, said the president was 鈥渃learly making a joke and then said, 鈥楢ll kidding aside.鈥欌

Following Biden鈥檚 poor performance during CNN鈥檚 presidential debate last week, some Democrats have begun to call for the president to drop out of the race, leaving the White House scrambling to convince skeptics within the party and voters. In the days after, administration officials have provided confusing and conflicting explanations as they attempted to spin a performance that exacerbated voters鈥 concerns about Biden鈥檚 age.

Following the meeting, Govs. Wes Moore of Maryland, Kathy Hochul of New York and Tim Walz of Minnesota painted a positive picture of the meeting during a news conference, adding that Biden is 鈥渁ll in鈥 and 鈥渋n it to win it.鈥

In response to a reporter鈥檚 question, Walz dismissed any concerns about Biden鈥檚 age and health, saying the president is 鈥渇it for office.鈥

Biden, the oldest president in US history, has faced questions around his age and health for years. They came to a head during the debate, when he was hoarse and at times unintelligible, leaving Trump 鈥 who is only three years younger than Biden 鈥 to appear more fit. The majority of debate watchers deemed the former president as the winner of the stand-off, according to a .

And Biden鈥檚 debate performance opened the floodgates for more scrutiny and reporting on the president鈥檚 health, with sources describing a decline in his mental fitness.

The New York Times reported earlier this week that the president鈥檚 鈥渓apses鈥 have increased and grown more worrisome, with a source telling the Times that Biden鈥檚 six-day debate preparations at Camp David didn鈥檛 start before 11 a.m. and that the president was given time to nap each day.

White House press secretary Karine Jean-Pierre sidestepped a question during Wednesday鈥檚 briefing about whether the president takes daily afternoon naps following the Times鈥 reporting. But she offered jet lag and travel fatigue as an explanation for Biden鈥檚 poor debate performance after previously chalking it up to a cold.

Amid increasing pressure to consider dropping out of the race and growing concern whether he can serve another term, CNN has previously reported that Biden has privately expressed that the next stretch of days will be critical for whether he can save his reelection bid.

CNN鈥檚 Kaanita Iyer, Jack Forrest, MJ Lee and Betsy Klein contributed to this report.