WASHINGTON

Former US President Donald Trump on Friday said he had a "big victory" during a presidential debate with President Joe Biden.

"As you saw on television last night we had a big victory against a man who is trying to destroy our country," Trump said at a rally in Chesapeake, Virginia.

His remarks came after Biden acknowledged his age and bad performance in the debate, but vowed to win the November election.

"It's not his age, it's his competence," Trump said, adding: "He's not respected anywhere in the world."

Biden's rambling answers and appearing to lose his train of thought in the debate heightened voter concerns that he might not be fit to serve another four-year term.

He told reporters following the debate that it is "hard to debate a liar," referring to Trump, and said the ex-leader lied 26 times.

The White House confirmed that Biden had a cold and sore throat during the debate. "He had the cold and had a sore throat. Again, he tested negative for Covid, and then we moved on," spokeswoman Karine Jean-Pierre told reporters.

Biden's Campaign Communications Director Michael Tyler said the strategy "doesn't change at all" after the debate.

Asked whether the president is committed to appearing at the debate with Trump in September, Tyler said: "Joe Biden will be there on Sept. 10. We'll see what Donald Trump does."