OAKLAND, Calif. — Two of San Francisco Bay Area Rapid Transit's largest unions went on strike after weekend talks with management failed to produce a new contract, ensuring a nightmarish journey ahead for Monday commuters.

The strike was called as Service Employees International Union Local 1021 and Amalgamated Transit Union Local 1555 workers' contracts expired at midnight Sunday. Both the unions and management earlier in the day said they were far apart on key sticking points including salary, pensions, health care and safety.

"I'm deeply disappointed it has come to this," SEIU negotiator Josie Mooney told reporters at a midnight news conference.

"Our members aren't interested in disrupting the Bay Area, but management has put us in a position where we have no choice," ATU Local President Antonette Bryant said.

Negotiations fell apart Saturday and the unions walked away from the table. California Gov. Jerry Brown's office had urged both sides to resume discussions Sunday with rush hour on the horizon. But talks between the two sides came to an end shortly before 8:30 p.m., when union negotiators left the state office building in Oakland that had been opened for the day as a neutral meeting ground.

BART accused union negotiators of walking away from the bargaining table while union negotiators countered that they had recessed to the union hall, and told management they had until midnight to offer a new proposal for them to consider.

The walkout is set to derail the more than 400,000 riders who use the nation's fifth-largest rail system and affect every mode of transportation. Transportation officials say another 60,000 vehicles could be on the road, clogging highways and bridges throughout the Bay Area.

The unions, which represent nearly 2,400 train operators, station agents, mechanics, maintenance workers and professional staff, were asking for a 5 percent annual raise over the next three years. BART said Saturday that train operators and station agents in the unions average about $71,000 in base salary and $11,000 in overtime annually. The workers also pay a flat $92 monthly fee for health insurance.

BART spokesman Rick Rice said BART had up its original offer of a 4 percent pay rise over the next four years to 8 percent. The proposed salary increase is on top of a 1 percent raise employees were scheduled to receive Monday, Rice added. .

The transit agency also said it offered to reduce the contribution employees would have to make to their pensions, and lower the costs of health care premiums they would have to pay.

Bryant said Sunday that BART's latest proposal is not an actual pay increase, calling it "surface bargaining."

BART's last strike lasted six days in 1997. The transit agency handles more than 40 percent of commuters coming from the East Bay to San Francisco with the Bay Bridge handling another 50 percent said John Goodwin, a spokesman for the Metropolitan Transportation Commission.

Other transit agencies in the region urged commuters to consider carpooling, taking buses or ferries, working from home and, if they must drive to work, to leave earlier or even later than usual.

San Francisco Mayor Ed Lee said the city will offer increased transportation options, including at the airport, and increase staff for traffic management. BART said it will let commuters use parking lots at their 33 stations free of charge for the purpose of carpooling.