Metro workers are threatening a "sick out" for this weekend. Sources tell News4 that Metro employees have been telling their supervisors they will not be going to work Friday.

Metro management and its largest union, ATU Local 689, are in a tense and ugly contract dispute. A union spokesman told News4 that members are "outraged" at the negotiations over the contract.

According to their contract, however, union members are not permitted to strike.

"Given the climate the [general manager] has set at WMATA, the union is looking at every possible legal tactic to get his attention," union spokesman David Stephen told News4.

However, union leaders said they do not support a sick out and don't believe that one will occur.

Nonetheless, supervisors are being told to be ready for 12-hour shifts.

"Due to the threat of a sick out for [ATU Local] 689 employees[,] all supervisors are required to work 12 hour shifts starting Friday April 28, 2017-April 30, 2017," according to an email sent to Metro supervisors Tuesday.

A Metro spokesperson said there has been an "unusually" high number of absence requests for this weekend.