As anxious commuters await word of a possible BART strike, both sides in the commuter rail's labor dispute remained optimistic that a deal would be reached even as they accused each other of stalling.

Bitter negotiations picked up on Monday, as the Bay Area's second-biggest transit operator faces a midnight Sunday deadline to reach a deal with its employee unions. As talks creep along, some 200,000 people who ride BART round-trip each weekday will be left wondering if the trains will stop running as soon as next week.

Workers will vote on Tuesday on whether to give union management the authority it needs to call a strike should the contract expire at the end of the month. But no dates for a strike have been set and both sides expect to return to the bargaining table throughout the week in hopes of reaching a deal.

 BART’s Daly City station.
BART's Daly City station. (Karl Mondon)

"We are talking settlement, we are talking agreement, we are bargaining," Antonnete Bryant, president of the local Amalgamated Transit Union, said while taking a break from negotiations Monday. "There has been some movement, but not significant."

BART said it was working with regional transportation officials on backup plans if it needs to shut down trains, including extra bus service that may be operated by BART.

"We're hopeful that it doesn't come to that," said Paul Oversier, BART's assistant general manager of operations. "We are doing the planning for it, but it's a little early right now."

On Monday, the ATU and the local SEIU -- BART's two largest employee unions -- said they filed a lawsuit in Alameda County Superior Court alleging the agency was unwilling to bargain over employee safety issues.

It comes after BART on Friday publicized the case of a station agent who prosecutors charged with filing a false police report about being attacked on the job. BART officials called the lawsuit a "smoke screen" to divert attention from other issues.

BART on Monday proposed a 4 percent pay hike across four years, a far cry from the 23 percent wage increase over three years that workers are seeking.

While the unions are looking for more safety measures and pay, agency management is trying to require workers to pay more money toward

their pension and health care benefits packages.

"We don't want a strike," Oversier said, "and we're going to do everything we can between now and midnight on June 30 to avoid a strike."

Contact Mike Rosenberg at mrosenberg@mercurynews.com or 408-920-5705. Follow him at Twitter.com/RosenbergMerc.