As some US states look to start reopening their coronavirus-battered economies amid protests from supporters of President Donald Trump anxious to get back to work, hardest hit New York state began mandating the wearing of masks or face coverings in public to contain the pathogen's spread.

The US Centers for Disease Control and Prevention (CDC) has reported 690,714 cases of coronavirus, an increase of 29,002 cases from its previous count, and said that the number of deaths had risen by 2,394 to 35,443.

The CDC reported its tally of cases of Covid-19, caused by a new coronavirus, as of 4pm (US Eastern Time) on 17 April, compared with its count a day earlier.

The CDC figures do not necessarily reflect cases reported by individual states. Some tallies put the nationwide cases at over 700,000.

Donald Trump said this evening that Texas and Vermont will allow certain businesses to reopen on Monday while still observing coronavirus-related precautions and Montana will begin lifting restrictions on Friday.

"We continue to see a number of positive signs that the virus has passed its peak," Mr Trump told reporters at a daily briefing.

Some state governors have warned, however, that they will not act prematurely to reopen their economies until there is more testing.

New York, epicentre of the US crisis, has reported another 540 coronavirus-related deaths, the lowest daily tally since 1 April.

While that was down from 630 a day earlier, it still represented hundreds more families who lost a loved one to Covid-19 in a single day in one state.

Thirty-six of the deaths occurred at nursing homes, which have been ravaged by the pandemic nationwide.

"It is the feeding frenzy for this virus," New York Governor Andrew Cuomo said during his daily coronavirus briefing.

Saturday ended another week in which millions of Americans went without paychecks. More than 20 million have filed for unemployment benefits in the past few weeks alone as closures of businesses and schools and severe travel restrictions have hammered the US economy.

One business deemed essential to keeping Americans fed that has been hit hard is meat processing plants.

Facilities in South Dakota, Georgia, Iowa and elsewhere have reported hundreds of infections among employees forced to work in close proximity, prompting some plants run by Tyson Foods and Smithfield Foods to shift production or shut, sparking calls by unions for safer working conditions.

Even with huge companies such as Walmart and Amazon hiring, some Americans who live in parts of states with lower infection rates have been made restless by restrictions that have left more than 90% of the country under stay-at-home orders, leading to protests this week by flag-waving Trump supporters in the capitals of Minnesota, Michigan and Virginia.

The demonstrations, which featured large crowds of people neither practicing social distancing nor wearing protective face coverings, angered governors who have been trying to bring coronavirus outbreaks in their states under control.

Read more Latest Covid-19 stories

Also angering those governors, all Democrats, were a series of Twitter posts on Friday by the Republican president that appeared to be egging on the protests.

While Trump agitates to get the country back up and running sooner rather than later as he faces re-election in November, the Pentagon announced it was extending travel restrictions for its personnel until the end of June.

Health experts have cautioned that to avoid a second wave of infections as people return to work, extensive testing must be available to track infections, as well as contact tracing and antibody testing to learn who had been previously infected.

Vice-President Mike Pence said on Friday that the United States had the capacity to do a sufficient amount of testing for states to move into a phase one of reopening.

However, governors and health officials in the states say there is nowhere near enough test kits and equipment available to do that kind of widespread testing.

Mr Cuomo on Saturday reiterated that federal funding was necessary for that magnitude of testing and to reopen the economy.

To help slow the virus' spread, New York has mandated statewide wearing of masks for anyone out in public and unable to practice social distancing. The rules, which cover all those using public transport or for-hire vehicles, came into effect on Friday night.

Mr Cuomo noted that while the number of patients needing intervention to help them breathe as the virus attacks their lungs has continued to decline, some 2,000 people were still being hospitalised with Covid-19 daily.

Still, there were signs of hope that the worst might be over, at least for New York.

"If you look at the past three days, you could argue that we are past the plateau and we're starting to descend, which would be very good news," Mr Cuomo said.

Other parts of the country have yet to see infections and deaths peak.

The United States has by far the world's largest number of confirmed coronavirus cases, with more than 700,000 according to some tallies of state-by-state figures.

The US tally of lives lost to Covid-19 has also soared to more than 35,000.

New York state accounts for nearly half those deaths.

"People are frustrated, we're anxious, we're scared, we're angry," Cuomo said.

"This is a terrible experience, it's disorienting, it threatens you to your core."

The US-Canada border will remain closed for another month to fight the spread of the pandemic.

"Canada and the United States have agreed to extend by another 30 days the border measures that are currently in place," Canadian Prime Minister Justin Trudeau said during his daily update on the crisis.

"This is an important decision and one that will keep people on both sides of the border safe."

The border crossing was originally scheduled to reopen on Tuesday.