WASHINGTON, DC, United States (AFP) — US President Donald Trump yesterday declared himself immune to COVID-19 and ready for a fight as his White House race against surging rival Joe Biden enters its critical final weeks.

Trump’s doctors gave him the all-clear Saturday to return to the campaign trail after he was ruled no longer a coronavirus transmission risk — although he has yet to be declared virus-free and his immunity claim is unproven.

“It looks like I’m immune for, I don’t know, maybe a long time and maybe a short time, it could be a lifetime, nobody really knows, but I’m immune,” Trump told Fox News show Sunday Morning Futures.

“The word immunity means something, having really a protective glow.

“So now you have a president who doesn’t have to hide in a basement like his opponent,” Trump added — in a jab at Democratic challenger Biden, who has taken a far more cautious approach to campaigning in a pandemic.

But it is not yet clear to what degree contracting COVID-19 confers immunity, with early studies suggesting a few months while newer ones have indicated it could last longer.

Twitter yesterday hid a tweet from Trump in which he claimed he was immune, saying the post violated its rules about misleading and potentially harmful misinformation.

The tweet was still visible once users clicked through the warning.

Trump, 74, was treated with Regeneron, an experimental antibody cocktail that may give immunity for just a few months when taken as a treatment rather than as a vaccine.

“In some cases, vaccines can last for decades. [But] if you get it in the form of natural immunity, that isn’t known yet,” Regeneron CEO Leonard Schleifer told CBS‘s Face the Nation yesterday.

“If you get it in our vial, if you will, that’s probably going to last you for months,” he said.

Badly trailing Biden with just 23 days until the November 3 vote, Trump has been counting the days until he can hit the trail again.

The Republican leader rallied hundreds of supporters for a comeback event at the White House on Saturday, and is planning back-to-back rallies this week — in Florida today, then Pennsylvania and Iowa — in a bid to salvage his struggling campaign.

During his phone interview on Fox News, Trump suggested that his White House rival could himself be sick.

“If you look at Joe, he was coughing yesterday horribly and grabbing his mask, as he’s coughing,” Trump said. “And I don’t know what that was all about, and it didn’t get much press.”

The Biden campaign has been publishing daily coronavirus tests for their 77-year-old candidate since Trump tested positive on October 1 — landing him in a military hospital for three nights and derailing his campaign.

There has been less transparency surrounding Trump’s own state of health, with his medical team repeatedly refusing to say when he last tested negative for the virus. That has fuelled suspicions that he may not have been tested for several days prior to his diagnosis.

COVID-19 has killed more than 214,000 people in the United States.

Biden has slammed Trump’s determination to rally huge crowds during the pandemic — but the president has brushed the concerns aside, insisting America has the upper hand against the virus.

“There is no excuse for President Trump’s reckless behaviour,” Biden tweeted again yesterday.

Barack Obama’s former vice -president is currently close to 10 points ahead in national polls with a solid lead in some key battleground states.

With his political horizon darkening, Trump has taken — more than ever — to recalling his surprise win in 2016, as if to persuade himself that he can pull off a second upset.

In a morning tweet yesterday he paraphrased the prominent statistician Nate Silver, who in 2016 called Trump’s victory “one of the most shocking events” in US history — firing back at him: “That’s only because you got it so wrong. This time there is far more enthusiasm even than 2016.”

“Big crowds!!!”