The Trump administration ramped up pressure on U.S. government workers on Thursday to accept a buyout offer ahead of a midnight deadline as labor unions urged members to remain in their jobs and sought to block the proposal in court.

The American Federation of Government Employees and two other unions claim the buyout offer is "arbitrary and capricious" and violates federal law, according to the complaint. The White House last week offered 2 million civilian full-time federal workers an opportunity to stop working this week and receive pay and benefits through Sept.