OAKLAND, Calif. — A chief negotiator said that two of San Francisco Bay Area Rapid Transit's largest unions will "likely" go on strike after contract talks stalled on Saturday.

Josie Mooney, a negotiator for the Service Employees International Union Local 1021, said there's "a 95 percent chance" that her union and members of the Amalgamated Transit Union Local 1555, will begin striking Monday after their contracts expire at midnight Sunday. The two unions represent nearly 2400 train operators, station agents, mechanics, maintenance workers and professional staff.

"I'm afraid I don't see a way we will avoid a strike," she said after union leaders left the negotiating table, claiming they have met with BART's management for only 10 minutes in the past 36 hours.

A walkout could derail the more than 400,000 riders who use the nation's fifth-largest rail system and affect every mode of transportation, clogging highways and bridges throughout the Bay Area.

Mooney said the unions have no plans to meet with BART on Sunday.

BART spokesman Rick Rice said Saturday says that the agency planned to attend talks scheduled for 11 a.m. Sunday and hoped union representatives will be there.

"The Bay Area is counting on us to come together and meet reasonably in the middle," he said in a statement issued late Saturday. "There is still time. Let's get it done."

Negotiations between BART and the unions had intensified as Sunday night's deadline loomed.

As the parties went back to the bargaining table Saturday in Oakland for anticipated around-the-clock sessions, both sides described the talks as tense and said they were far apart on key sticking points including salary, pensions, health care and safety.

The unions want 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.

Rice said BART offered a 4- to 8 percent salary raise over the next four years, on top of a 1 percent raise employees were scheduled to receive Monday. The transit agency also offered to reduce the amount of employee contributions it originally requested for pension and medical benefits.

On Friday, the ATU asked California Gov. Jerry Brown to issue a 60-day "cooling off" period if no deal can be reached by Sunday's deadline, but the SEIU and BART officials have urged Brown not to issue such an order.

The governor's office has declined to comment.

"Negotiations are frustrating," Rice said. "But, we'll be here, no matter long it takes. We're committed to work this out."

BART's last strike lasted six days in 1997. On Friday, other area transit agencies 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.

"The bottom line is that a BART strike will be an absolute nightmare for everyone," said Jim Wunderman, president and CEO of the Bay Area Council, a business advocacy organization. "Our transportation system simply does not have the capacity to absorb the more than 400,000 BART riders who will be left at the station. There will be serious pain."