The number of confirmed coronavirus cases in the United States has topped one million, representing almost a third of the global total.

The milestone comes as the US death toll from the novel coronavirus exceeds the 58,220 American lives lost during the Vietnam War.

US cases have doubled in 18 days and make up one-third of all infections in the world, according to a Reuters tally.

The actual number of cases is believed to be higher, with state public health officials warning that shortages of trained workers and materials have limited testing capacity.

The news came as about a dozen states moved to restart their economies despite a lack of large-scale virus testing.

President Donald Trump’s economic adviser has forecast an unemployment rate of more than 16 per cent for April and protests have been breaking out over stay-at-home orders.

While most US states seem to have passed their peaks in the pandemic, seven — Hawaii, Mississippi, Texas, Wyoming, Utah, Nebraska and North Dakota — may be experiencing their peaks now or in the coming weeks, the model shows.

The number of Americans seeking unemployment benefits over the past five weeks has soared to 26.5 million, underscoring the pandemic’s economic impact.

Chuck Schumer, the top US Senate Democrat, said state and local governments would be forced to make “massive” layoffs if Congress did not act soon to assist with the costs of addressing the pandemic.

Georgia, at the vanguard of states re-opening businesses, has allowed restaurant dining for the first time in a month.

Texas governor Greg Abbott said he would let the state’s stay-at-home order expire and begin re-opening businesses, including dining venues and retail shops, in phases at the end of the week.

Florida Governor Ron DeSantis met with Mr Trump at the White House and said he would make an announcement this week about how to relax restrictions in his state.

The governors of other states, including New York, have deferred easing restrictions out of concern they might fuel a second wave of infections.

“Everyone is talking about reopening. I get it,” New York governor Andrew Cuomo said, adding decisions should not be based on politics, emotions or in reaction to protests.

“We want to reopen, but we want to do it without infecting more people or overwhelming the hospital system,” he said.

This sign says it all. Keep your face covered when you’re in public and can’t maintain social distance. pic.twitter.com/yiISqZSbhI

— Andrew Cuomo (@NYGovCuomo) April 28, 2020

About 30 per cent of the cases have occurred in New York state, the epicentre of the US outbreak, followed by New Jersey, Massachusetts, California and Pennsylvania.

The US death toll since the first death recorded on February 29 reached 58,233 on Tuesday, up more than 2000 from the prior day.

The outbreak could take more than 74,000 US lives by August 4, compared with an April 22 forecast of over 67,600, according to the University of Washington’s predictive model often cited by White House officials.

Globally, coronavirus cases top three million since the outbreak began in China late last year.

The US, with the world’s third-largest population, has five times as many cases as the next hardest-hit countries of Italy, Spain and France.

Of the 20 most severely affected countries, the US ranks fifth based on cases per capita.

The US has about 30 cases per 10,000 people. Spain ranks first at over 48 cases per 10,000 people, followed by Belgium, Switzerland and Italy.

The coronavirus deaths in the US fall short of the approximately 100,000 Americans killed by seasonal flu in 1967, according to the CDC.

It is also far less deadly than the Spanish flu, which began in 1918 and killed 675,000 Americans.

-with agencies