Detroit"s Big Three automakers are not yet mandating vaccines for thousands of unionized workers even as they said in a joint statement with the United Auto Workers on Tuesday that they will extend requirements for workers to wear masks at work sites. General Motors Co (GM.N), Ford Motor (F.N), Chrysler-parent Stellantis and the UAW said they have agreed that unionized auto workers will be asked to report vaccination status on a voluntary basis, but not as a requirement. They also agreed to continue mask requirements at work sites. The White House wants employers to mandate vaccinations. Labor Department rules issued Nov. 5 requiring all companies with 100 or more employees to mandate vaccines or regular testing by Jan. 4 for nearly all employees have been put on hold by a federal appeals court. On Tuesday, the Biden administration asked a court to lift the stay. "Vaccination requirements work. They’re implementable without disruptions. And they boost — they boost dramatically vaccination rates," White House COVID-19 response coordinator Jeff Zients said on Monday. The UAW has resisted suggestions it agree to vaccine mandates. UAW President Ray Curry in September told members that "until the various rules described above are finalized, the UAW’s bargaining position continues to be that vaccination is strongly encouraged, but a personal choice." Biden has worked hard to win the autoworkers’ support, in part because UAW members are crucial to winning elections in Michigan and other Midwestern states. But the UAW’s reluctance to support vaccination mandates reflects a broader resistance among many unions to the Biden administration’s policies. Last week, Stellantis said it would require all of its 14,000 U.S. salaried non-union employees to be fully vaccinated against COVID-19 by Jan. 5, as it prepares for a phased reopening of its U.S. offices next year. Most, but not all, of the salaried workforce of U.S. automakers is not unionized. Nearly 80% of its salaried non-union U.S. workforce self-reported that they are fully vaccinated, Stellantis said. Earlier this month, Ford said it would require most of its 32,000-strong U.S. salaried workforce to be vaccinated. The second largest U.S. automaker earlier this month said more than 84% of U.S. salaried employees already are vaccinated. Ford said earlier it was still evaluating its policy for "manufacturing locations, parts depots and Ford Credit, including analyzing federal and collective bargaining requirements." GM, Ford and Stellantis said last month they would mandate vaccines for all autoworkers in Canada. GM declined to say Friday if it would require vaccines for U.S. salaried employees.