WASHINGTON (AFP, REUTERS) - Donald Trump's chief of staff said on Friday (Oct 2) that he was optimistic about a rapid recovery for the president as he confirmed that Trump has "mild symptoms" after testing positive for Covid-19.

"The President and the First Lady... remain in good spirits," Mark Meadows told reporters.

"The President does have mild symptoms and, as we look to try to make sure that not only his health and safety and welfare is good, we continue to look at that for all of the American people."

He said there would be updates on Trump's health later on Friday.

One such update, from Trump's election campaign manager Bill Stepien, was that the president's election campaign events would be either postponed or held virtually.

The US election will be held in 31 days, on Nov 3. Polls show Trump trailing his Democratic opponent, former vice-president Joe Biden.

Meadows added that "the American people can rest assured that we have a president that is not only on the job, (but) will remain on the job, and I'm optimistic that he'll have a very quick and speedy recovery.

"I'm not going to get into any particular treatment that he may or may not have. He has mild symptoms. As we we look at that, the doctor will continue to provide expertise in the residence. He is in the residence right now."

Trump's doctor earlier said the President and his wife were "well".

Melania Trump tweeted on Friday: "I have mild symptoms but overall feeling good. I am looking forward to a speedy recovery."

Trump earlier on Friday announced via Twitter that he and his wife had tested positive for Covid-19.

Vice-President Mike Pence and his wife tested negative, a Pence spokesman said.

The White House official said Pence would work from his own residence several miles from the White House and his staff was being kept separated from Trump's staff "out of an abundance of caution."

Pence, 61, a conservative former US lawmaker and Indiana governor, would take over if Trump were to become incapacitated.

The president's illness upended his re-election campaign with just 31 days left to go until the presidential election.

Polls show Trump trailing his Democratic opponent, former vice-president Joe Biden.

Biden said on Twitter that he and his wife Jill wished Trump and the first lady a speedy recovery. "We will continue to pray for the health and safety of the president and his family," he said.

Biden is expected to be tested on Friday and Democratic vice-presidential nominee Kamala Harris tested negative on Thursday, according to a person familiar with the matter.

Just hours before Trump's announcement, the president had proclaimed the pandemic almost over, while Biden had tweeted accusing Trump of trying to distract from a "failed Covid-19 response" that led to the deaths of more than 200,000 Americans from the disease.

Trump is at high risk because of his age and weight. He has remained in good health during his time in office but is not known to exercise regularly or to follow a healthy diet.

The Republican National Committee would chose a replacement nominee if Trump were to become incapacitated, but it is already too late in most states to change the names on the ballot.

Millions of ballots have been sent out to voters and at least 2.2 million people have already voted, according to figures compiled by University of Florida professor Michael McDonald.

CAMPAIGN CRISIS

Trump understated the seriousness of the coronavirus outbreak in its early stages and has repeatedly predicted it would go away. He rarely wears a mask and regularly mocks others including Biden for wearing them so often.

Trump advisers acknowledged that they would have to rip up their plans for the final weeks of the election campaign. Trump has held in-person rallies with supporters who mainly decline to wear masks, and has taunted Biden for avoiding such events.

"Trump is a high-energy president with a giant personality. Without his persona, the campaign is missing its energy," Republican fundraiser Dan Eberhart said.

Trump's positive test also means that others at the highest levels of the US government have been exposed and may have to quarantine, too. Meadows said all core White House staff has been tested with negative results, and another White House official said contact tracing was under way.

International leaders and US politicians on both sides of the aisle offered sympathy to Trump but his estranged niece Mary Trump took a swipe at him for his handling of the response to the pandemic.

"I reserve my sympathy, empathy, and despair for those who are sick and for those who have died because they were misled, lied to, or ignored," she wrote on Twitter.

Trump is the latest world leader to be tested positive for the virus, which can cause a severe respiratory infection.

British Prime Minister Boris Johnson kept working in isolation for around a week after testing positive in March but then fell gravely ill and was rushed into intensive care. He spent several weeks recovering before returning to work.

Canadian Prime Minister Justin Trudeau went into quarantine in March after his wife was diagnosed with the coronavirus.

Brazilian President Jair Bolsonaro called the virus a "little flu" after being infected in July.

On Thursday night, shortly after Trump predicted the pandemic's end was in sight, news broke that Hope Hicks, a top adviser and trusted aide, had tested positive for the virus.

Hicks travelled with the president on Air Force One on Tuesday and Wednesday.

Trump flew to New Jersey after White House officials learned of Hicks's symptoms, and attended a fundraiser at his golf club and delivered a speech. Trump was in close contact with other people, including campaign supporters, at a roundtable event.

The president's condition is likely to bring the pandemic back to center stage in the race, after the death of Supreme Court Justice Ruth Bader Ginsburg shifted the campaign's focus.

Trump, who has been criticised for questioning the efficacy of wearing a face covering, produced a mask from his pocket in his first debate against Biden on Tuesday and said, "I wear masks when needed. When needed, I wear masks."

He then ridiculed the former vice-president for putting one on regularly: "I don't wear masks like him. Every time you see him, he's got a mask. He could be speaking 200 feet away from them and he shows up with the biggest mask I've ever seen," Trump said.

The White House has had previous coronavirus scares. Pence's spokeswoman, Katie Miller, tested positive earlier this year and suffered symptoms before recovering.

But the White House lowered its precautions as Trump sought to project a return-to-normality message this summer.

Temperature checks of everyone entering the White House complex stopped, and while coronavirus tests continued for people who came into close proximity to Trump, others on campus were not tested.