U.S. President Joe Biden again called his debate against Republican opponent Donald Trump "a bad episode," but remained resolute in an interview with ABC News on Friday that he was the candidate to beat Trump in November's election.

"No indication of any serious condition. I was exhausted. I didn't listen to my instincts in terms of preparing and -- and a bad night," Biden, 81, told ABC News anchor George Stephanopoulos in a taped interview in Madison, Wisconsin.

"I just had a bad night. I don't know why," Biden added in a hoarse voice, stumbling occasionally over his words.

Biden was gently but repeatedly probed by Stephanopoulos about whether he was being realistic in his belief that he could beat Trump, giving widening polls between the two and growing concern from elected Democrats.

"I don't think anyone is more qualified," Biden told Stephanopoulos in the interview. The polls, he said, were inaccurate.

Asked whether he would drop out if fellow Democrats in Congress said he was hurting their re-election chances in November, Biden said: "If the Lord Almighty comes out and tells me that I might do that."

The 22-minute interview, which Stephanopoulos said was not cut or edited, was being closely watched by Democrats concerned about the president's ability to serve another four years, or beat Trump, 78, in the election, after his faltering debate performance on June 27.

A senior House of Representatives Democratic aide, who declined to be named, told Reuters after watching a short clip aired before the interview: "I don't see how he (Biden) lasts the week as the nominee."

COGNITIVE TEST

"I was feeling terrible," Biden said. "Matter of fact the docs with me. I asked if they did a COVID test because they're trying to figure out what was wrong. They did a test to see whether or not I had some infection, you know, a virus. I didn't. I just had a really bad cold."

He added that it was no one else's fault but his own, and that he hadn't rewatched his debate performance.

Asked whether he was more frail, Biden said, "No."

"Look, I have a cognitive test every single day. Every day I have that test – everything I do (is a test)," Biden said as he was repeatedly asked about whether he would take a cognitive test.

Earlier on Friday, Biden told a crowd in a fiery speech in Madison that some Democrats were trying to push him out of the race in the wake of the debate with Trump. But he said during the ABC News interview that senior Democrats would not ask him to step aside.

He said he spoke for an hour with House Speaker Hakeem Jeffries from New York and longer with Representative Jim Clyburn from South Carolina.

During the interview, Biden highlighted his record in office, saying that he expanded NATO (the North Atlantic Treaty Organization), grew the economy and has a peace plan for the Middle East. He talked about expanding healthcare and making changes to the tax system if he won a second term.

The interview, even before it aired in full, seemed to do little to assuage viewers about Biden's age.

"I've seen enough," Ron Fournier, senior adviser with communications agency Truscott Rossman and former White House correspondent, said on social media platform X alongside the clip. "It hard to imagine this good man beating Trump and serving four more years in the most demanding job on earth."