Hospitals bracing for a possible surge of coronavirus patients worry they could face a shortage of ventilators. Now other companies may step in to help.

WASHINGTON — Tesla and Space X CEO Elon Musk pledged on Twitter that his companies will make ventilators, if there is a shortage at hospitals because of the coronavirus pandemic.

The Society of Critical Care Medicine projects that 960,000 coronavirus patients in the U.S. may need to be put on ventilators at one point or another during the outbreak. But the nation has only about 200,000 of the machines, by the organization's estimate, and around half are older models that may not be ideal for the most critically ill patients.

The Pentagon said this week it would be giving 5 million respirators and 2,000 ventilators to Health and Human Services to be used for virus response.

FiveThirtyEight editor-in-chief Nate Silver challenged Musk on the exact number that he was planning to make and why they weren't already making these crucial supplies.

"Tesla makes cars with sophisticated hvac systems. SpaceX makes spacecraft with life support systems. Ventilators are not difficult, but cannot be produced instantly," Musk replied.

Musk's pledge comes after White House economic adviser Larry Kudlow revealed Wednesday night on FOX News that General Motors Chairman and CEO Marry Barra had offered to build hospital ventilators at GM's idled plants.

A GM spokesman confirmed to Forbes that the company's CEO indicated to the White House that it was something they were exploring and "beginning to look into it."

Ford, General Motors, Fiat Chrysler, Honda and Toyota said on Wednesday they would shut down all factories in the region, citing concerns for employees who work in close quarters building automobiles. Nissan is closing U.S. factories.

According to the CDC, patients diagnosed with this coronavirus experience a mild to severe respiratory illness. Symptoms include fever, cough and shortness of breath.

In mainland China, where the virus first exploded, more than 80,000 people have been diagnosed, but more than 60,000 already have recovered. Patents with severe complications from the virus often develop pneumonia in both lungs.