Janitors and security officers in the Twin Cities are expected to vote Saturday to authorize a strike if negotiators for their union and their employers fail to reach agreements.

More than 6,000 workers are seeking higher wages and more affordable health care in separate contract talks as the Service ­Employees International Union (SEIU) negotiates with contract maintenance firms that clean and provide security for some of the metro area's largest companies.

SEIU Local 26 members are employed by contractors who service some high-profile corporate buildings including Target Corp., Medtronic, Wells Fargo Center, Wells Fargo Mortgage and U.S. ­Bancorp Bank Plaza.

A strike could have a significant impact because this is the first time that both the union's janitors and security ­officer contracts expired at the same time, said Kate Brickman, media relations manager for the SEIU Minnesota State Council. The SEIU members have been working without a contract since Dec. 31 while negotiating in separate ­bargaining committees, according to Local 26. The strike authorization vote would give the ­bargaining committees the power to call a strike.

"We simply believe that those who clean and protect these multimillion dollar properties should be treated fairly and should be able to make a living and support their families," SEIU Local 26 President Javier Morillo said Tuesday at a news conference at the downtown Minneapolis Hilton.

The union says the contractor side of the table has been less than cooperative.

"Our members have been ready to come to the table for months, looking for improvements in our contract. Yet our employers just want to step backwards," said Fred Anthony II, who is a security officer at the Ecolab headquarters in St. Paul and a member of the security officer bargaining committee. "They don't want to bargain in good faith. They really just seem like they want to gut our union."

David Duddleston, a spokes­man for the security contractors including American Security, AlliedBarton and Securitas, said the employers have offered a number of dates and the parties have agreed to some but not all of them.

"Our perspective is that the union had difficulties scheduling meetings," Duddleston said. "It's complicated to have a multiple number of companies bargaining at the same time. We're trying on both sides to meet in good faith."

A federal mediator has been brought into the security ­officer contract negotiations.

"We're firmly committed to bargaining in good faith and reaching an agreement to the benefit of employees, employers, and the customers that we both serve," said John Nesse, the chief negotiator for nine janitorial contractors, including ABM, Marsden, and ­Harvard Maintenance.

Nesse said the Affordable Care Act has created significant issues at the janitorial bargaining table, but he declined to elaborate.

The union has underscored the connection their members have to high-profile companies and buildings in the Twin Cities.

"Companies like Target and U.S. Bank will try to distance themselves," said John Budd, an industrial relations expert at the University of Minnesota's Carlson School of Management. "The question is how successfully they will manage to distance themselves."

A heightened public awareness of the link these Minnesota business heavyweights have to a strike could put contractors in a difficult situation, Budd said.

"The contractor doesn't want to put Target in a situation where they feel their public image is under attack," Budd said. "On the other side, if they settle for too high of an agreement, that's not good for the contractor."

Said Morillo, the Local 26 president: "As always we are hoping for the best, no one wants to strike. But we are, especially given the status of the negotiations, most certainly prepared for the worst."

Justin Miller is a University of Minnesota student reporter on assignment for the Star Tribune.