California has declared a state of emergency after announcing its first coronavirus death, bringing the US death toll from the disease to 11.
The 71-year-old man, who died in a hospital near Sacramento, had underlying health conditions and had been on a cruise ship, said officials.
The White House moved on Wednesday to expand testing nationwide for the disease.
There are now at least 150 reported US patients with Covid-19 in 16 states.
Authorities have confirmed more than 92,000 cases of the virus worldwide, of which more than 80,000 are in China. More than 3,000 people have died globally, the vast majority in China.
Ten of the 11 US deaths were in Washington state, but the outbreak has also flared up in Texas and Nebraska.
Washington and Florida both declared states of emergency over the weekend to help prevent the coronavirus.
The California man who died is believed to have been exposed to the disease while travelling last month on a Princess Cruise ship that departed from San Francisco and visited Mexico.
The vessel has been ordered to return to port in San Francisco.
The ship is operated by Carnival, whose Diamond Princess cruise liner was quarantined last month after dozens of passengers tested positive for Covid-19 as it docked in Japan.
Testing speeded up
US Vice-President Mike Pence said on Wednesday that any American can be tested for the coronavirus if ordered by a doctor.
Mr Pence, appointed by President Donald Trump to lead the US outbreak response, also said that the White House will begin on-camera briefings on the virus.
Some health officials have accused the Trump administration of a slow-footed response to the outbreak.