Members of BART’s two largest unions representing train operators, mechanics, station agents and maintenance workers voted Tuesday to authorize a potential strike, union officials said.

More than 98 percent of voting members of the Service Employees International Union, Local 1021 and 99.9 percent voters from the Amalgamated Transit Union, Local 1555, approved a strike vote.

Despite the vote, the two unions representing some 2,300 members say they’re committed to negotiating a new contract with BART and currently have no immediate plans to walk out after their contract expires late Sunday night.

“We’re not trying to strand the Bay Area,” said ATU Local President Antonette Bryant before heading to another bargaining session. “All we want is fair compensation and a safe workplace.”

A new strike would affect hundreds of thousands of daily commuters, virtually affecting every mode of transportation throughout the Bay Area.

Jim Wunderman, president and CEO of the Bay Area Council, a business advocacy organization, said when BART’s last strike occurred in 1997 for six days, 275,000 commuters were affected, causing untold misery. Now about 400,000 riders use BART each weekday.

A transit stoppage would bring “serious pain,” Wunderman added, especially to those who live in the East Bay and work in San Francisco, the Penisula and Silicon Valley.

“A BART strike would be disastrous, crippling our transportation system and economically paralyzing the entire region,” Wunderman said. “Employers should prepare for the worst, and BART and the unions should buckle down and get a contract done.”

In the event of a strike, the Metropolitan Transportation Commission plans to help increase other transportation options such as buses and ferries. This, despite the union representing some 1,800 Alameda-Contra Costa Transit workers could also go on strike as early as next week as its contract also expires on Sunday.

BART spokesman Rick Rice said Wednesday that its unions’ strike authorization vote was expected.

“We’re prepared to negotiate as much and as often and as long as they want to,” Rice said. “We’ll continue to work to get a deal done.”

The unions are asking for raises adding up to about 23.2 percent over three years. BART has offered 1 percent raises, contingent on the agency meeting economic goals, in each year of the four-year contract it’s proposed.

“We’ve still got a lot of talking to do,” Rice said referring to the huge gap concerning pay.

The unions also say they’re fighting management’s efforts to have workers contribute to pensions, pay more for health insurance, and help reduce overtime expenses.

The opposing parties remain optimistic however that a deal can be reached, despite the unions’ filing a lawsuit on Monday against BART seeking an unfair labor practices declaration and claims the transit agency is not bargaining in good faith.

Employees currently pay a flat $92 fee each month for health insurance, no matter the plan or how many people are covered. Rice said the agency wants to increase that payment, but he offered no details on an amount.

The transit agency also said it needs to control costs to help pay for new rail cars and other improvements. The unions contend BART has a $125 million operating surplus, and members deserve some of it for increased ridership and high service reliability rates.

“The money is there for them to do their capital projects and still give us the decent pay raise, benefits and health and safety measures that we’re asking for,” Bryant said.

The unions would not have to give the agency notice before calling a strike, but reiterated on Wednesday that they would give the public a 72 -hour notice.