"I am, somewhere. I don't know when," the Democratic president said in an interview with broadcaster Howard Stern.
"I'm happy to debate him."
The remarks were Biden's clearest yet on the prospect of a presidential debate.
Biden had not previously committed to debate Trump, saying last month it would depend on the former president's behaviour.
Donald Trump says he is ready to debate President Joe Biden "anytime, anywhere, anyplace". (AP PHOTO)
Trump, who refused to debate his rivals before winning the Republican primary race last month, has in recent weeks been challenging Biden to engage in a one-on-one match-up with him, offering to debate the incumbent Democrat "anytime, anywhere, anyplace".
Earlier this month, Trump's top two campaign advisers sent a letter to an independent commission that normally sanctions such events calling for an accelerated debates timetable, holding more than the usual three and starting them earlier in the campaign cycle.
A dozen leading US news organisations have also urged the candidates to publicly commit to debating each other.
Their statement suggested that debates for the current race be sponsored, as they have every election cycle since 1988, by the non-partisan Commission on Presidential Debates.
Biden's camp has been concerned that once on stage Trump will not abide by rules set by the Commission, and some Biden advisers say they would prefer not to elevate Trump by putting him on the same stage with the Democratic incumbent.
Asked during a trip to Las Vegas in early February about Trump calling for Biden to debate him, Biden said, "If I were him, I would want to debate me too. He's got nothing to do".
Biden and Trump faced each other in two televised presidential election debates during the 2020 campaign.
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