Donald Trump has challenged Joe Biden to TV debates, as the rivals hurtle towards a White House rematch following their sweep of the Super Tuesday votes.
The Republican said he would take part in a TV forum with the Democratic president "anytime, anywhere, anyplace" posting online in all capital letters.
Mr Biden's campaign said Mr Trump was "thirsty for attention and struggling to expand his appeal".
No debates have so far been agreed ahead of November's election.
Mr Trump's challenge came hours after his last Republican rival, Nikki Haley, dropped out of the race to be the Republican nominee for the White House.
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"It is important, for the Good of our Country, that Joe Biden and I Debate Issues that are so vital to America, and the American People," Mr Trump posted on his social media website, Truth Social, hours after Ms Haley's departure from the race.
He added that such debates could be run by the Democratic National Committee, or the Commission on Presidential Debates, which has overseen presidential debates for the last 30 years.
Mr Trump said the debate commission - which declares itself non-partisan, but is accused by conservatives of bias - was a "subsidiary" of the Democratic party.
Mr Trump, 77, has repeatedly claimed Mr Biden, 81, is too old and forgetful to debate him. Mr Biden has in turn suggested it is Mr Trump who is senile.
The White House press secretary was asked earlier on Wednesday whether refusing a debate could cast doubt on Mr Biden's "acuity". She suggested the reporter speak to the president's re-election campaign.
The Biden campaign did not say whether he would participate in a debate against Mr Trump, and instead suggested that the Republican tune in to the president's Thursday evening State of the Union address to Congress.
"That's a conversation we'll have at the appropriate time in this cycle," said Biden campaign communications director Michael Tyler.