(CNN) -- Transit workers in California's Bay Area warned Thursday that they will go on strike Sunday at midnight local time if no progress is made in contract negotiations.
A previous strike over the same negotiation deadlock paralyzed the San Francisco regional transportation system for four days in July.
Bay Area Rapid Transit management said there was no good reason for the strike.
"A strike only stalls and delays the decisions that need to be made while using our riders as pawns," it said.
Unions accuse BART management of refusing to negotiate in good faith.
"It is unfortunate that we find ourselves in the same situation that we were in 30 days ago, with no real progress made by management to address worker concerns about safety and wage cuts," union president Roxanne Sanchez said in a statement.
BART denies the claim of wage cuts, saying that its contract offer contained a yearly raise.
Unions originally asked for a 21% pay increase. BART initially offered to increase salaries by 4% over four years, but later proposed an 8% increase, which was on top of a previous 1% increase.
Spokesman Rick Rice accused union representatives of being unreasonable by continuing to insist upon the same pay raise.
"The future of the system depends on a more reasonable contract," he said.
Negotiations will continue through Sunday in hopes of averting another shutdown.
No trains ran then, and BART implemented a limited charter bus service to accommodate commuters.
BART is the nation's fifth-largest train system, with 44 stations in 26 cities that make up the Bay Area, according to the transit authority.
About 400,000 people use the service daily.
CNN's Melissa Gray contributed to this report