Ford, GM and Tesla have been given the “go ahead” to make ventilators to help alleviate a shortage amid the COVID-19 pandemic, President Donald Trump said in a tweet Sunday that ended with a challenge to auto executives to show how good their companies are.

Ventilators are a critical piece of medical equipment for patients who are hospitalized with COVID-19, a respiratory disease caused by coronavirus. COVID-19 attacks the lungs and can cause acute respiratory distress syndrome and pneumonia. And since there is no clinically proven treatment yet, ventilators are relied upon to help people breathe and fight the disease. There are about 160,000 ventilators in the United States and another 12,700 in the National Strategic Supply, the NYT reported.

The tweet follows a plea Sunday morning from NY Gov. Andrew Cuomo for the federal government to nationalize medical supply acquisition instead of leaving it to individual states. Cuomo is one of a growing group of officials to call for Trump to order companies to produce medical supplies under the Defense Production Act, a law that allows the federal government to compel private industry to produce materials needed for national defense.

Without the nationalization, states are competing against each other for supplies, Cuomo said. Prices have spiked as a result, putting more pressure on a health care system.

Trump has issued an executive order that invokes the Defense Production Act, but it’s unclear if it has been used. Trump said last week during a press conference that it had been, but Federal Emergency Management Agency head Peter Gaynor told reporters Sunday that the president has not yet ordered any companies to make more critical supplies.

I’m calling on the Federal Government to nationalize the medical supply chain. The Federal Government should immediately use the Defense Production Act to order companies to make gowns, masks and gloves. Currently, states are competing against other states for supplies. — Andrew Cuomo (@NYGovCuomo) March 22, 2020

Several automakers said last week they were looking into the feasibility of producing ventilators. GM said Friday that it is working with Ventec Life Systems to help increase production of respiratory care products such as ventilators that are needed by a growing number of hospitals as the COVID-19 pandemics spreads throughout the U.S. The partnership is part of StopTheSpread.org, a coordinated effort of private companies to respond to COVID-19, a disease caused by coronavirus.

Ford told TechCrunch in an email Sunday that it stands ready to help the administration, including the possibility of producing ventilators and other equipment.

“We have had preliminary discussions with the U.S. and U.K. governments and looking into the feasibility,” the Ford spokesperson Rachel McCleery said. “It’s vital that we all pull together to help the country weather this crisis and come out the other side stronger than ever.”

SpaceX and Tesla CEO Elon Musk tweeted Saturday that he had a discussion with Medtronic about ventilators. Medtronic later confirmed those talks in a tweet. He had previously tweeted that SpaceX and Tesla will work on ventilators, without providing specifics.

Tesla could not be reached for comment.