TOKYO -- The U.S. Embassy in Japan says Americans aboard a quarantined cruise ship will be flown back home on a chartered flight Sunday.

About 380 Americans are aboard the Diamond Princess cruise ship, which has docked at Yokohama, a port city southwest of Tokyo. So far, 285 people from the ship have tested positive for a new virus, after 67 new cases, including three more Canadians, were found Saturday.

The aircraft will arrive in Japan late Sunday, and people will be flown to Travis Air Force Base in California, with some passengers continuing to Lackland Air Force Base in Texas, the embassy said in a letter to passengers and crew that was posted online Saturday.

After arriving in the U.S., all will need to go through another two weeks of quarantine, the letter said.

Everyone will get a checkup before being allowed on the chartered flight, and those who show symptoms of sickness will not be permitted to board the plane, the embassy said.

"We recognize this has been a stressful experience and we remain dedicated to providing all the support we can and seeing you safely and expeditiously reunited with family and friends in the United States," it said.

One of the American passengers, Matthew Smith, who has been tweeting aboard the ship, including photos of the food passengers have been given, expressed disappointment at what he called "a monkey wrench" the American government was throwing into the quarantine that he and others had tried to maintain on the ship.

Smith said he'll have to start the 14-day quarantine period all over again even though he was due to get off the ship next week.

"OK, so here's the thing: As long as the official plan by Japanese health officials is to release those of us who are still healthy from quarantine in just under four days, why would I want to interfere with that by taking up an offer from U.S. officials to fly us back to Travis?" he said on Twitter.

The letter to Americans on the Diamond Princess warns, "Should you choose not to return on this charter flight, you will be unable to return to the United States for a period of time."

Japan's Health Ministry allowed 11 passengers to disembark Friday, saying that those over 80 years old with underlying medical conditions as well as those staying in windowless cabins during the 14-day quarantine can stay at a designated facility on shore.

That quarantine was set to be over as soon as Wednesday, meaning people might be able to leave the boat as long as they were healthy.

Separately, the Japanese government said Saturday that a chartered flight to bring Japanese out of Wuhan -- the Chinese city at the centre of the outbreak of the virus -- will leave Sunday and return Monday. That would be the fifth such plane for Japan.

Besides the cases on the cruise ship, Japan has reported 55 other cases. Three new cases were reported Saturday in Wakayama prefecture in central Japan, and eight others were reported in Tokyo.