Los Angeles -- The number of confirmed US coronavirus cases soared past 500 Sunday, including two further deaths, as President Donald Trump defended his administration's "perfectly coordinated" response to the epidemic.

The surge came as medics headed to a cruise ship off the California coast to prepare passengers for landfall, and Senator Ted Cruz went into self-quarantine after shaking hands with an infected person.

Some 30 US states have been hit by the novel coronavirus, with Oregon the latest to declare an emergency, and 60 million people in California and New York under crisis measures.

Two more deaths linked to a virus-hit care home near Seattle were reported Sunday, bringing the nationwide toll to at least 21.

In an early-morning tweet, Trump, who has been accused of peddling misinformation on the outbreak, blamed the media for trying to make his government "look bad."

"We have a perfectly coordinated and fine tuned plan at the White House for our attack on CoronaVirus," he tweeted.

"We moved VERY early to close borders to certain areas, which was a Godsend. V.P. is doing a great job. The Fake News Media is doing everything possible to make us look bad. Sad!"

But Larry Hogan, the Republican governor of Maryland, criticized Trump, telling NBC the president "hasn't communicated the way I would, and the way I might like him to."

Fellow Republican Cruz revealed he had shaken hands at a conservative conference with a person who later tested positive.

"I have decided to remain at my home in Texas this week, until a full 14 days have passed," he wrote on Facebook, adding he had no symptoms.

Trump and Vice President Mike Pence also attended the Conservative Political Action Conference (CPAC) near Washington last month.

'Unprecedented and difficult' 

A Johns Hopkins tally put the number of confirmed US cases at 537 by Sunday afternoon, with newly diagnosed patients in states including Pennsylvania, Illinois, Massachusetts, Connecticut and New Jersey.

Medical officers on Sunday headed for the virus-hit cruise ship stranded off California to begin screening passengers for an "unprecedented and difficult" landing operation.

The Grand Princess, with 21 confirmed coronavirus infections among 3,500 people on board, is due to dock in Oakland Monday after four days off the coast of nearby San Francisco.

The operation to move passengers ashore will take two to three days, said Governor Gavin Newsom.

Carolyn Wright, a passenger on board, told AFP that people without symptoms were allowed to leave their cabins for the first time since Thursday.

Once ashore, ill passengers will be moved to hospitals, while Americans not requiring treatment will be quarantined at military bases in California, Texas and Georgia for 14 days.

Several hundred foreign passengers, representing 54 nationalities, will be repatriated.

Of 237 Canadians on board, those without symptoms will be flown to Trenton, Ontario for quarantine, Ottawa said.

The Regal Princess -- another cruise ship owned by the same company -- was reportedly held off the Florida coast Sunday as two crew members who transferred from the Grand Princess were tested.

The State Department warned vulnerable people including the elderly "should not travel by cruise ship."

'Flat-footed'

Trump has been heavily rebuked for repeatedly contradicting the advice of his administration's experts in his public pronouncements about the coronavirus.

He has downplayed the threat posed by the epidemic, which has killed more than 3,500 people since emerging in China, suggesting cases were "going very substantially down, not up."

New York Governor Andrew Cuomo said federal health authorities had been "caught flat-footed" and had "handcuffed" the ability of individual states to respond.

"Their messages are all over the place, frankly," he told Fox News.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told Fox News that the possibility of following Italy's example in locking down large sections of the population could not be ruled out.

"You don't want to alarm people but, given the spread we've seen, anything is possible," he said.