A transit strike entered its third day Wednesday after the governor refused to intervene and the transportation agency angered workers by voting to hire an out-of-state security firm for half a million dollars.

Nearly 1,750 bus drivers, light-rail operators and mechanics walked off the job early Monday in the Denver area's first transit strike in nearly a quarter century. Only limited bus service has continued on a system that averaged 275,000 rides a day.

Representatives of both sides planned to sit down informally Wednesday with a federal mediator to try to resolve the stalemate.

The union had asked Gov. Bill Owens to order binding arbitration, but he refused on Tuesday and blamed the strike on union leaders who had unanimously recommended the proposed contract but didn't convince their members to approve it. Fifty-five percent of workers rejected the offer.

"They failed and now the public is suffering because of that failure," Owens said.

The governor's decision came amid growing resentment in the union after the Regional Transportation District approved spending $500,000 to hire a Cleveland-based security firm.

"They got the money, have them push it this way," union leader Yvette Salazar said. "Put it to the workers and keep the money in Colorado. Why send it out of state?"

RTD general manager Cal Marsella said the security measure was pre-emptive but necessary to protect employees, facilities and equipment.

The contract offer that transit workers rejected included a wage hike of about $1.80 an hour over three years plus increases in health benefits. Union officials said the workers want more upfront money built into the pact because their wages have been frozen since 2003.

The transit authority runs bus and light-rail systems in Denver and all or parts of seven surrounding counties, a service area with about 2.5 million residents. This week, the RTD has operated about 45 percent of its bus routes by using private contractors.

Even with more commuters left to rely on car pools and taxis, traffic had flowed smoothly along interstates and major roads, a highway department spokesman said.