Tucson bus riders could find long waits this week if a contract between Sun Tran drivers and the company that manages the bus system isn’t reached by Wednesday night.

Negotiations for a new contract stalled over the weekend after union members rejected an offer from Professional Transit Management, the company that operates Tucson’s bus system. Union officials say they want the company to reinstate a wage progression system that gives drivers a yearly pay increase for the first four years of employment.

PTM ended automatic wage increases for drivers two years ago.

Andy Marshall, one of the negotiators with the Teamsters Local 104, which represents Sun Tran drivers, said talks between the union and company officials will continue with the hopes of avoiding a strike.

“We don’t want to go into details about why we’ve rejected it because we’re still negotiating, hoping to resolve it prior to the expiration," he said.

The current contract expires Wednesday at midnight.

In a statement, Sun Tran officials said that in the event of a strike, only limited weekday service on routes 3, 4, 6, 8, 11 and 16 will be available.

A strike by Sun Tran drivers will not affect operation of the Sun Link streetcar, Sun Van, Sun Shuttle, and the Downtown Loop.

Roughly 1.5 million people use the Sun Tran bus system each month.