Detroit's three big automakers are shifting into a partial shutdown mode at their factories amid a push by the United Auto Workers union for more stringent measures to protect workers from becoming infected with the coronavirus.

General Motors  (GM) - Get Report, Ford  (F) - Get Report and Fiat Chrysler  (FCAU) - Get Report have agreed to rein in production, with "rotating partial shutdown" of auto plants, as well as deep cleaning of factories between shifts and longer periods between them, among other measures. This as the industry braces for the onslaught of covid-19, the United Auto Workers said in a statement.

The decision by the car-and-truck manufacturers will affect roughly 150,000 auto workers across the U.S. It appears to be a move to head off union calls for a complete two-week shutdown.

GM on Monday closed its Tech Center in Warren, Mich., which employs 20,000, after an employee there tested positive for the coronavirus.

A showdown between the union and the automakers began gathering steam on Sunday when UAW President Rory Gamble warned that the union would take unilateral action unless the Big Three took more action to protect workers from covid-19.

The automakers have already sent their white-collar workforces home, allowing them to work remotely.

Shares of the three auto makers on Wednesday slumped as markets went into another steep dive following Tuesday's short-lived rally.

At last check GM dropped 21% to $16.15 a share, followed by Fiat Chrysler, which gave up 12% to $6.71, and Ford, which fell 10% to just under $4.50.

Separately, GM said it would take a $1.1 billion first-quarter charge that will extend through 2020 as it moves ahead with plans to wind down sales, design and engineering operations in Australia and New Zealand.