In a memo released by the White House, Navy Cmdr. Dr. Sean Conley said Trump meets the Centers for Disease Control and Prevention criteria for safely discontinuing isolation and that by "currently recognised standards" he is no longer considered a transmission risk, reports AP.

However, it was not clear whether this meant that he had tested negative for Covid-19 as the memo did not declare Trump as testing negative for the virus. But sensitive lab tests — like the PCR test — detect virus in swab samples taken from the nose and throat.

Dr. William Morice, who oversees laboratories at the Mayo Clinic, said earlier this week that using the PCR tests, the president's medical team could hypothetically measure and track the amount of virus in samples over time and watch the viral load go down.

On Saturday, the president delivered a speech in front of cheering supporters at the White House in his first public appearance since being hospitalised with the virus, reports BBC.

There had been concerns that he might still be contagious following his three-day hospital stay.

Saturday's event was officially a "peaceful protest", but looked, critics said, much like a Trump campaign rally.

The president, who says he is no longer taking medicines against Covid-19, told the crowd he was "feeling great".

His rival in next month's presidential election, Joe Biden, has been campaigning in Pennsylvania. He said his "heart goes out" to all those families who have lost someone they love to coronavirus.

Polling suggests Mr Biden has a single-digit lead over Mr Trump and an ABC News/Ipsos poll found that just 35 percent of Americans approved of how Mr Trump has handled the coronavirus crisis.

More than 210,000 Americans are known to have died of Covid-19.

What were the concerns over the event?

Questions over safety were raised after a gathering to unveil Mr Trump's nominee to the Supreme Court resulted in at least 11 people subsequently testing positive for Covid-19 - including the president. Top US infectious disease expert Dr Anthony Fauci described it as "a super-spreader event".

Senior Democratic Congressman Adam Schiff said it was "morally bankrupt" for the president to hold "another super-spreader rally" at the White House.

The White House said in advance of Saturday's event that those attending would be required to undergo a temperature check and wear face masks, and encouraged to practice social distancing.

However, images from the event showed several hundred people packed closely together.

The president's campaign team has also said he is planning to attend a "big rally" in Florida - a battleground state in next month's presidential election - on Monday, followed by trips to Pennsylvania and Iowa.

Mr Biden expressed disbelief at the president's plans to hold rallies and criticised the Trump administration's lax stance on mask use as reckless. "I wouldn't show up unless you have a mask and can distance," Mr Biden said, speaking while campaigning in Las Vegas on Friday.

Meanwhile, ethics experts say that hosting political events at the White House, as well as being against long-standing convention in the US, could violate federal law.

The Hatch Act, dating from 1939, bars federal employees from being involved in campaign activities while on duty. While the president and vice-president are exempt, most White House employees are not.

On Thursday Sean Conley said that it would be safe for Mr Trump to return to public engagements on Saturday [October 10] as that would mark "day 10" since his diagnosis on Thursday 1 October.

Following his diagnosis, Mr Trump spent three nights in hospital and was treated with the steroid dexamethasone, the antiviral drug remdesivir and a cocktail of manufactured antibodies made by the company Regeneron.

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