"Stay tuned," Biden told reporters at the White House.

Neither the White House, the Democratic Party nor the president himself have confirmed he will announce but multiple US media reports, citing unnamed sources, say the move will come early Tuesday in a video address.

"I'll let you know real soon," Biden told reporters when asked about an announcement.

The date would fall exactly four years after Biden announced his candidacy for the 2020 election in which he defeated Donald Trump. That too was made in the low-key format of a video, as was Barack Obama's 2012 re-election campaign announcement.

By contrast, Trump formally launched his bid for a second term in 2019 at one of his signature rallies.

Trump, 76, has also already announced his bid for a 2024 comeback and is the strong frontrunner to be the Republican Party's nominee, despite having been criminally indicted and remaining under multiple other investigations on serious allegations.

Biden's Tuesday schedule currently features an address on the economy at a Washington hotel conference room.

While not a campaign event, the scheduled theme -- "how his investing in America agenda is bringing manufacturing back, rebuilding the middle class, and creating good-paying union jobs" -- is set to be at the heart of the Democrat's 2024 message.

In the evening, Biden and First Lady Jill Biden will visit Washington's Korean War Memorial along with South Korean President Yoon Suk Yeol and his wife Kim Keon Hee, as they kick off a state visit -- and give Biden an opportunity to highlight his foreign policy record.

- Low enthusiasm -

History shows that as the incumbent, Biden would have an immediate advantage.

Trump, dragged down by his management of the Covid-19 pandemic and fears among many swing voters that he was a threat to democracy, was the first sitting president in three decades to lose re-election.

Biden is also presiding over a powerful post-pandemic economic revival -- usually a key factor in deciding presidential elections.

However, he faces unique headwinds. Chief among these is worry over his age.

He'd be 82 when he began his second term and 86 when he left office. At 80, he is already the oldest person ever in the Oval Office.

An official medical report this year found Biden to be physically in good condition.

But the president's noticeably slow walk -- notwithstanding his habit of throwing in a few steps at a jog -- and his frequent moments of becoming tongue tied during public speaking have spooked even supporters.

An NBC News poll released over the weekend found that 70 percent of Americans, including 51 percent of Democrats, believe he should not run for a second term. Forty eight percent cited concerns over his age as the main reason and another 21 percent cited that as a minor reason.

Among those raising strong doubts over Biden's fitness to serve another grueling four years after this term ends was The New York Times editorial board last week.

"The president also needs to talk about his health openly and without embarrassment, and to end the pretense that it doesn't matter," it said.

Asked about the issue, Biden always replies "watch me" -- explaining that voters should look not at his age but his record of delivering several historic investment bills, leading a coalition to support Ukraine against Russian invasion, and other achievements during a drama-filled first term.