United States President Donald Trump on Friday appeared to support protesters in some states demanding an end to restrictions designed to stop the spread of the coronavirus.

His relationship with New York Governor Andrew Cuomo also swerved downhill as he hit back at Mr Cuomo's criticism of federal assistance to his state, which has been hit hardest by the virus.

The heated rhetoric has come on top of worries over lifting stay-home orders too quickly.

Mr Trump said on Friday: "I think 29 states… (will be) able to open relatively soon."

He did not name the states. But Florida and Texas have already eased or are set to ease some restrictions.

"Every day we're getting closer to the future that we all have been waiting for," Mr Trump said. "We are getting very, very close to seeing that light shine very brightly at the end of that tunnel."

The President and his allies have been chafing at the economic damage from restrictions deemed necessary by public health experts to curb the spread of the deadly Covid-19, which as of yesterday morning had killed more than 37,000 people in the US.

On Friday, Mr Cuomo slammed the federal government for not providing adequate assistance - financially and in obtaining medical equipment through international supply chains.

But the President shot back in a tweet saying Mr Cuomo should spend more time "doing" and less time "complaining".

On Thursday, Mr Trump unveiled a three-phase plan to reopen the country, contingent on states or regions showing a downward trend in documented infections for 14 days before they can begin the first phase of reopening.

Among other conditions, hospitals should be treating all patients without crisis care and have robust testing for health workers.

But the guidelines do not provide any national plan for increasing testing capacity, which experts say needs to be dramatically scaled up before it is safe to lift restrictions.

The US is currently testing roughly 145,000 people daily, according to data compiled by the Covid Tracking Project.

"We still probably need to be doing three times more testing than we're doing now," Dr Ashish Jha, director of the Global Health Institute at Harvard told the Associated Press. "I don't see America getting by any time soon with 100,000 to 150,000 tests."

A backlash against restrictions is growing in more conservative parts of the country. Minnesota and Michigan were among the states that saw protesters - some armed and some waving pro-Trump placards - demanding that restrictions be lifted.

"Liberate Minnesota", the President tweeted on Thursday, followed quickly by "Liberate Michigan". In a third tweet, he said: "Liberate Virginia", adding, "and save your great Second Amendment. It is under siege!"

The Second Amendment gives citizens the right to bear arms.

Last week, Virginia expanded background checks and imposed new limits on gun purchases.

The three states, plus Ohio, Wisconsin, Texas and Oklahoma, have this past week seen small protests comprising mostly pro-gun rights, pro-Trump, and anti-vaccine and anti-government overreach groups.

Many are battleground states. Mrs Hillary Clinton won Virginia and Minnesota in 2016. Michigan is expected to be hotly contested.

The President's tweets were flayed by Democrats, though Republicans have remained largely silent - for fear, analysts say, of being targeted by the mercurial President.

Governor Jay Inslee of the state of Washington said in a statement: "The President's statements… encourage illegal and dangerous acts. He is putting millions of people in danger of contracting Covid-19.

"The President is fomenting domestic rebellion… even while his own administration says the virus is real and is deadly, and that we have a long way to go before restrictions can be lifted."

The University of Washington's Institute for Health Metrics and Evaluation (IHME), which has been modelling the spread of the virus, on Friday said only a few states should consider reopening by May 4 including Vermont, West Virginia, Montana and Hawaii.

Others such as Iowa, North Dakota, South Dakota, Nebraska, Utah, Arkansas and Oklahoma may need to wait until June or July, it said.

In a statement, IHME director Christopher Murray cautioned: "Relaxing social distancing too soon carries great risks of a resurgence of new infections. No one wants to see this vicious cycle repeating itself."