Trump has invoked the Korean War-era Defense Production Act, which allows a president to force companies to make products for national defence.

Mr Trump said that "GM was wasting time" and action was needed to save American lives.

The US now has 104,000 cases of the virus, the most in the world.

With nearly 1,700 fatalities, America's Covid-19 death toll still lags far behind Italy and China.

Mr Trump had previously said the defence order was not necessary, because companies were voluntarily converting their operations to help fight the spread of coronavirus.

But on Friday he said in a statement: "The virus is too urgent to allow the give-and-take of the contracting process to continue to run its normal course."

Earlier in the day he took to Twitter to complain that GM lowered the number of ventilators they had promised to deliver from 40,000 to 6,000 and had wanted "top dollar".

He also criticised GM chief executive Mary Barra, saying things are "always a mess" with her at the helm of the Detroit-based auto manufacturer.

Twtter : Donald J. Trump

@realDonaldTrump

General Motors MUST immediately open their stupidly abandoned Lordstown plant in Ohio, or some other plant, and START MAKING VENTILATORS, NOW!!!!!!  FORD, GET GOING ON VENTILATORS, FAST!!!!!!  @GeneralMotors  @Ford

GM said on Friday it can build at least 10,000 ventilators per month from April.

What's the background to the row?

GM has been working with a Seattle-based medical device manufacturer, Ventec Life Systems, to build ventilators at the car maker's plant in Kokomo, Indiana.

GM's factory in Warren, Michigan, will be used to make surgical masks, the Associated Press reported.

The White House had been due to announce the joint venture between the two companies on Wednesday until Trump administration officials reportedly baulked at the $1bn bill to taxpayers.

During the coronavirus task force briefing on Friday, the president said: "We're not looking to be ripped off on price."

Mr Trump also acknowledged he was "extremely unhappy" over the closing of GM's plant in Lordstown, Ohio.

The car-maker sold the factory last November, axing 1,400 jobs in a key presidential swing state.

Why the need for ventilators?

The medical machines that keep patients breathing are much in demand amid the respiratory illness' outbreak, which in the most serious cases attacks the lungs.

Louisiana's governor said on Friday that New Orleans could run out of ventilators by 2 April.

The Society of Critical Care Medicine has estimated that 960,000 intensive care patients will require a ventilator at some point during the US coronavirus outbreak.

New York has requested 30,000 ventilators, but Mr Trump said during Friday's briefing he felt that was a "high" estimate.

New York Governor Andrew Cuomo fired back, insisting the request was based on "facts and on data".

What's happening with New York?

The state remains the epicentre of the Covid-19 crisis in the US, with over 7,000 new cases announced on Friday alone. There are a total of 44,000 patients thus far, and the death toll has climbed to 519.

For the first time since the 9/11 attacks, New York City has been preparing makeshift mortuary space, readying refrigerated lorries to help hospitals as the death toll rises.

This week governors in Florida, Maryland, South Carolina, Rhode Island and Texas have ordered visitors from the New York area to self-quarantine for at least 14 days upon arrival. The neighbouring state of Connecticut has implored New Yorkers to keep away altogether.

On Friday, Rhode Island police began pulling over vehicles with New York registration plates to obtain contact information in order to enforce the mandatory 14-day quarantine.

Is Trump handling the crisis well?

A Washington Post poll this week found 48% of Americans approve of the president's work and 46% disapprove - the highest approval and lowest disapproval ratings of his term.

But former US Vice-President Joe Biden, who looks likely to be Mr Trump's Democratic challenger in the November presidential election, on Friday said Mr Trump had "ignored the warnings for months" and "downplayed" the threat of the pandemic.

"It's one of the greatest failures of presidential leadership in our history," Mr Biden tweeted.

What's happening elsewhere in the US?

Cable channel Fox Business has fired primetime television programme host Trish Regan after she claimed earlier this month the coronavirus crisis was a Democratic "scam" to impeach President Trump

A physician and assistant professor at the University of Connecticut has been arrested after he was accused of intentionally coughing on colleagues

The attorney general of Texas on Friday issued a legal opinion deeming gun stores "essential services" during the pandemic - firearm shops across the US have reported soaring sales thanks to Covid-19

The owner of a restaurant in Naples, Florida, is searching for a mystery customer who quietly left a $10,000 cash tip to help out staff