A cruise ship on which at least 21 people are infected with coronavirus will dock in Carlifornia and unload its passengers – despite Donald Trump saying he wanted them to stay on board to keep the number of US cases down.

The Grand Princess is expected to arrive in Oakland on Monday. It has been anchored off San Francisco for several days.

So far 19 employees and two passengers have tested positive for Covid-19. Another 24 people tested negative and one case was inconclusive. There are about 3,500 passengers on board.

On Friday, Mr Trump said he wanted to keep passengers and crew on board so that US cases would not "double".

He said: "They would like to have the people come off. I'd rather have the people stay. But I'd go with them. I told them to make the final decision. I would rather – because I like the numbers being where they are. I don't need to have the numbers double because of one ship that wasn't our fault."

The US currently has more than 400 confirmed cases of Covid-19, with 19 deaths.

Virginia has now reported two cases, including a US Marine, the first American military personnel to have the virus on US soil.

On Saturday evening the mayor of Washington DC, Muriel Bowser, confirmed the first case in the capital, a man in his 50s with no history of recent international travel and no close contacts to anyone known to have the virus.

The captain of the Grand Princess, John Smith, in a recording by a passenger quoted by the Associated Press, said: "An agreement has been reached to bring our ship into the port of Oakland.

"After docking, we will then begin a disembarkation process specified by federal authorities that will take several days."

Passengers who need medical treatment will be taken to healthcare facilities in California, while state residents who don't require acute medical care "will go to a federally operated isolation facility within California for testing and isolation".

American passengers from other states will be transported by the federal government to facilities elsewhere. Crew members will be quarantined and treated aboard the ship. It was not immediately clear what would happen to foreign nationals on board the liner.

On Sunday morning, Mr Trump – who has faced criticism for repeatedly trying to play down the crisis and for his administration's response -- tweeted: "We have a perfectly coordinated and fine tuned plan at the White House for our attack on CoronaVirus. We moved VERY early to close borders to certain areas, which was a Godsend.

The Grand Princess cruise ship anchored off San Francisco, California (REUTERS)

"V.P. is doing a great job. The Fake News Media is doing everything possible to make us look bad. Sad!"