The US Navy has fired the captain of an aircraft carrier who faced a growing outbreak of the new coronavirus on his ship, saying he created a panic by sending his memo pleading for help to too many people.

Key points: Captain Crozier will be removed from his post, but will keep his rank and remain in the Navy

Captain Crozier will be removed from his post, but will keep his rank and remain in the Navy He had asked to remove all but 10 per cent of his crew as the virus spread through the ship

He had asked to remove all but 10 per cent of his crew as the virus spread through the ship Democrats on the House committee issued a joint statement in support of Captain Crozier

In a four-page memo to Navy leaders, the captain of the nuclear-powered warship said the spread of the disease was ongoing and accelerating, and said that removing all but 10 per cent of the crew was a "necessary risk" in order to stop the spread of the virus.

Navy Secretary Thomas Modly said the ship's commander Brett Crozier "demonstrated extremely poor judgment" in the middle of a crisis.

He said the captain copied too many people on the memo, which was leaked to a California newspaper and quickly spread to many news outlets.

Captain Crozier will be removed from his post, but will keep his rank and remain in the Navy, Mr Modly said.

That decision was immediately condemned by members of the House Armed Services Committee, who called it a "destabilising move" that would "likely put our service members at greater risk and jeopardise our fleet's readiness".

Mr Modly told Pentagon reporters during an abruptly called press conference that Captain Crozier should have gone directly to his immediate commanders, who were already moving to help the ship.

He said Captain Crozier created a panic by suggesting 50 sailors could die.

Captain Crozier graduated from the US Naval Academy in 1992 and later attended the Nuclear Power School, a prerequisite to command a nuclear-powered aircraft carrier.

The USS Theodore Roosevelt, with a crew of nearly 5,000, is docked in Guam, and the Navy has said as many as 3,000 people will be taken off the ship and quarantined by Friday.

More than 100 sailors on the ship have tested positive for the virus, but none have been hospitalised.

The USS Theodore Roosevelt is docked in Guam, and the Navy has said thousands will be taken off the ship and quarantined. ( AP: Bullit Marquez, file )

"What it does, it undermines our efforts and the chain of command's efforts to address this problem and creates a panic and creates the perception that the Navy is not on the job, the Government is not on the job, and it's just not true," Mr Modly said.

He complained that Captain Crozier sent the memo to people outside his chain of command and in a non-secure, unclassified email.

He concluded that the captain's ability to react professionally was overwhelmed by the coronavirus challenge, "when acting professionally was what was needed most".

"We do, and we should, expect more from the commanding officers of our aircraft carriers," he said.

Mr Modly said he had no information to suggest Captain Crozier leaked the memo to the press. But he said that if Captain Crozier had communicated only with his leadership and not widely distributed the memo, he would likely still have a job.

Democrats in support of Captain Crozier

Democrats on the House committee issued a joint statement in support of Captain Crozier.

They said that while the captain went outside his chain of command, the pandemic presented a new set of challenges.

"Captain Crozier was justifiably concerned about the health and safety of his crew, but he did not handle the immense pressure appropriately," the statement said.

"However, relieving him of his command is an overreaction."

Captain Crozier, in his memo, raised warnings the ship was facing a growing outbreak of the coronavirus and asked permission to isolate the bulk of his crew members on shore, an extraordinary move to take a carrier out of duty in an effort to save lives.

He said that removing all but 10 per cent of the crew would be a "necessary risk" in order to stop the spread of the virus.

"We are not at war. Sailors do not need to die. If we do not act now, we are failing to properly take care of our most trusted asset: our sailors," Captain Crozier wrote.

Stay up-to-date on the coronavirus outbreak Download the ABC News app and subscribe to our range of news alerts for the latest on how the pandemic is impacting the world

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 20 minutes 20 m The Virus

ABC/wires