WASHINGTON

Former US President Barack Obama on Friday backed President Joe Biden after his poor performance during Thursday night's presidential debate against Donald Trump.

"Bad debate nights happen. Trust me, I know," Obama said on X.

In the first US presidential debate of 2024, Biden, who was Obama's vice president from 2009-2017, seemingly struggled to talk, tripped over his words, misspoke and lost his train of thought.

The debate reignited concerns among Democrats about the 81-year-old’s fitness for another term in office.

"But this election is still a choice between someone who has fought for ordinary folks his entire life and someone who only cares about himself," Obama said.

"Between someone who tells the truth; who knows right from wrong and will give it to the American people straight — and someone who lies through his teeth for his own benefit. Last night didn’t change that, and it’s why so much is at stake in November."

Biden has acknowledged age and bad debate performance, but vowed to defeat Trump during the elections on Nov. 5.

"I know I'm not a young man. I don't walk as easy as I used to. I don’t speak as smoothly as I used to. I don’t debate as well as I used to, but I know what I do know — I know how to tell the truth," he told a rally in North Carolina on Friday.