United States President Donald Trump said Monday that he is "upset" with China over a lack of cooperation and information early on in the coronavirus crisis.

"They should have told us about this," Trump told a regular press conference at the White House.

"I'm a little upset with China. I'll be honest with you..., as much as I like President Xi and as much as I respect the country and admire the country," he said.

Trump meanwhile said he had ordered the deployment of emergency medical stations with capacity of 4,000 hospital beds to coronavirus hotspots around the US.

Trump told a news conference that he had told the FEMA emergency management agency to set up the medical stations in New York, California and Washington state.

He said eight stations in California would have 2,000 beds and that four stations for both New York and Washington state would have a total of 1,000 beds each.

"I want to assure the American people that we're doing everything we can each day to confront and ultimately defeat this horrible invisible enemy," he said.

"We're at war, in a true sense we're at war," Trump added.

The US has almost 33,000 confirmed cases of COVID-19, with 409 deaths, according to a running tally by Johns Hopkins University.

Trump said he had approved a request to issue a major disaster declaration for the state of New York, which has seen the vast majority of America's coronavirus cases.

He added that he had approved one for Washington state as well and would do the same for California "very shortly."

Trump told reporters during his now-daily White House briefing on the pandemic that the federal government would pay for National Guard soldiers to be deployed in the three states to help contain the spread of the virus.

He added that the US Army Corps of Engineers would help build the temporary medical sites in New York and that the US Navy hospital ship USNS Mercy would be deployed to Los Angeles.