A US federal appeals court has temporarily halted the Biden administration's vaccine requirement for businesses.
The mandate requires workers at businesses with 100 or more employees be fully vaccinated by January 4 or face mask requirements and weekly tests.
More than half of the US states with Republican governors or attorneys general had filed suits with courts to stop it.
The 5th Circuit Court of Appeals, based in New Orleans, which has jurisdiction over the states of Mississippi, Louisiana and Texas, suspended the mandate on Saturday citing potential "grave statutory and constitutional" issues.
The Biden administration has to respond by Monday.
Some local governments and businesses in the United States have already required their workers to get vaccinated.
But there is strong opposition from people who see the moves to get the pandemic under control as violating their individual freedom.