YOKOHAMA, Japan — Japan said on Tuesday it had completed tests on a coronavirus-riddled cruise ship docked near Tokyo, as those free of the disease hoped to spend their last night aboard before disembarking.

The Diamond Princess has become a particularly virulent breeding ground for the new coronavirus, with at least 454 infections among the 3,700 passengers and crew — easily the second-biggest global cluster outside the Chinese epicenter.

Britain became the latest country to offer its citizens a way off the boat, saying it was "working to organize a flight back to the UK" as doubts grow over the effectiveness of the quarantine measures with every spike in positive cases.

Canada, Australia, Hong Kong and South Korea have already said they will evacuate their citizens from the ship, following the lead from the United States, which flew home around 300 Americans on Monday — including more than a dozen who had tested positive.

"We have done tests for everyone (on the ship)," Japanese Health Minister Katsunobu told reporters.

"Some results have already come out... and for those whose test results are already clear, we are working to prepare disembarkation," he said.

In a letter sent to passengers, authorities explained that some test results would take time to process and that therefore "we plan the disembarkation to take place from 19 to 21 February."

"If you and your roommate are both negative and have no fever of respiratory symptoms, you will be able to prepare for disembarkation," the letter said.

But those who had close contact with anyone who tested positive will have their quarantine reset to that date.

The crew, some of whom have complained about their conditions on board, are also expected to remain to observe another quarantine period after the last passengers leave the ship.

Japan has been forced to defend its policy amid criticism for the way it handled the situation, with dozens of new infections detected almost daily since the ship arrived in early February.

The Americans already evacuated will have to undergo another 14-day quarantine in the United States.

Canada said Tuesday it had arranged a chartered flight to repatriate nationals from the Diamond Princess, but gave no details when it would take place.

There were 256 Canadians on board the ship, with 32 so far testing positive for the virus.

South Korea will send a presidential aircraft on Tuesday to fly back four nationals and one Japanese spouse, an official told reporters.

There are 14 South Koreans on board, but the other ten have declined to be evacuated because they live in Japan, the Yonhap news agency reported.

While foreign governments have couched their decision to remove citizens as an attempt to reduce the burden on Japanese authorities, many have interpreted the evacuations as tacit criticism of Tokyo's handling of the situation.

The US and Australia have told citizens that if they decline repatriation and an additional 14-day quarantine, they will not be allowed home for at least two weeks, suggesting they do not believe the ship-based quarantine worked.

Japan has also confirmed at least 74 cases domestically — including many involving people with no history of recent travel to China.

Authorities have said the virus is being transmitted locally now, and have asked citizens to avoid crowds and non-essential gatherings.

On Monday, the amateur portion of the Tokyo Marathon — which had been expected to attract some 38,000 runners — was canceled. Only elite athletes will now be able to take part.

The public celebration for Emperor Naruhito's birthday has also been scrapped over virus fears. — AFP