Apple, GM and Tesla are among the U.S. firms diversifying from their specialist areas to help deliver essential medical supplies like masks and ventilators to assist in the fight against the novel coronavirus.

Why it matters: Testing capacity for COVID-19 has expanded in the U.S., as demand for medical equipment increases. Leading medical associations expressed concern in a letter to President Trump Saturday that "there will not be enough medical supplies, including ventilators, to respond to the projected COVID-­19 outbreak."

Doctors have reported a shortage of N95 fitted masks, "a necessary tool to prevent healthy people from getting sick because they help block 95% of microbes," notes Axios' Marisa Fernandez.

Case numbers surged to 26,747 in the U.S. early Sunday — the third-highest in the world after China and Italy.

Leading the charge: An Apple spokesperson told Axios that the tech giant would donate millions of masks to authorities worldwide — including 2 million to the Trump administration to distribute around the U.S. and a further 1 million to California's government.

President Trump praised Hanes clothing company at a White House briefing Saturday for "retrofitting its manufacturing capabilities in large sections of the plants to produce masks and they're in the process right now."

clothing company at a White House briefing Saturday for "retrofitting its manufacturing capabilities in large sections of the plants to produce masks and they're in the process right now." Tesla CEO Elon Musk, who has previously downplayed the coronavirus, said his company would provide 250,000 masks to California hospitals, Gov. Gavin Newsom (D) told a news conference Saturday.

who has previously downplayed the coronavirus, said his company would provide 250,000 masks to California hospitals, Gov. Gavin Newsom (D) told a news conference Saturday. Tesla is in talks with medical device company Medtronic to make "state-of-the-art ventilators," Musk tweeted Saturday.

with medical device company Medtronic to make "state-of-the-art ventilators," Musk tweeted Saturday. American brewer Anheuser-Busch announced Saturday it's using its supply and logistics network to begin producing and distributing bottles of hand sanitizer.

announced Saturday it's using its supply and logistics network to begin producing and distributing bottles of hand sanitizer. GM and Ventec Life Systems announced in a statement Friday that they are collaborating, in cooperation with StopTheSpread.org, the nation's coordinated private sector response to the COVID-19, "to enable Ventec to increase production of its respiratory care products" including ventilators.

announced in a statement Friday that they are collaborating, in cooperation with StopTheSpread.org, the nation's coordinated private sector response to the COVID-19, "to enable Ventec to increase production of its respiratory care products" including ventilators. GM and Ford both confirmed Thursday they were in talks with the Trump administration about the possibility of making such medical equipment to assist in the fight against the virus.

both confirmed Thursday they were in talks with the Trump administration about the possibility of making such medical equipment to assist in the fight against the virus. Freight logistics firm Flexport has "successfully sourced and is buying around $1.4 million worth of face-masks and other medical protective equipment that were requested by San Francisco's Department of Public Health," per Axios' Dan Primack.

The big picture: Trump invoked the Defense Production Act in order to help get medical supplies where needed.

A White House official told Axios' Alayna Treene the president is using the Defense Production Act to drive the private-sector’s response to this crisis. "[T]he private-sector’s response, to date, to his direction has been overwhelming, fulfilling government-identified needs faster than anyone thought possible," the official said.

Vice President Mike Pence said at the briefing Saturday the Department of Health and Human Services had "placed an order for hundreds of millions of N95 masks," though it's unclear when these would arrive.

Go deeper: Delivery date of medical masks to doctors, nurses unclear