Union officials declined to give the margin of victory but said the 11,000 members who went to the polls Sunday voted overwhelmingly in favor of strike authorization. The measure needed a two-thirds vote to pass.

Despite the vote, a strike could not start until the week of April 9. Under the terms of a three-week contract extension, which the union and the supermarkets agreed to last week, there can be no work stoppage during that time.

After the contract expires, it will extend on a day-to-day basis, and either side must give 72-hour notice to cancel the contract. Only then could union officials call for a strike.

Albertsons, Ralphs and Vons have been trying to negotiate a new deal with the United Food and Commercial Workers union through a federal mediator. The current contract helped end a bitter 4 ½-month strike and lockout in 2004.

In a statement, Albertsons called the strike vote unfortunate because the two sides were still working to craft a new deal. There are 22,000 Albertsons workers in Southern California.

“With the strike authorization now in place, a strike can be called against Albertsons without any additional discussion with our employees,” the statement said. “We do not believe that this is in the best interests of the employees or our ongoing negotiations.”

Mickey Kasparian, head of UFCW Local 135 in San Diego and Imperial counties, said the vote sends a clear message to Albertsons and the other chains.

“The vote proves that our membership is as united as ever,” he said.

The union has said it selected Albertsons because it is the company with which it has had the most contract talks and because the union views the newly acquired chain as more vulnerable. Supervalu, the nation's third-largest grocery chain, bought Albertsons last year and is working to incorporate the new stores into its operations.

Harley Shaiken, a professor at the University of California Berkeley who specializes in labor issues, said the strike vote will put pressure on Albertsons to come up with a deal by April 9.

“It will certainly get the employers to notice,” he said. “It establishes the deadline as having some significance.”

George Whalin, CEO of Retail Management Consultants in San Marcos, said the strike vote doesn't give the union any undue leverage because both sides will do anything to avoid a costly repeat of the ugly labor dispute of three years ago.

“I don't think they are going let it come to that,” he said of a possible strike. “They've got to find some common ground.”

The key issues are wages, health benefits and the possible elimination of a two-tier system. That system, which was put in place as part of the last contract agreement, stipulates that new hires get paid less and have to work longer to qualify for benefits.

Even though the strike authorization vote prevailed, the union complained that Albertsons used inappropriate measures to try to dissuade employees from voting in favor of the proposal.

The union said Albertsons held mandatory meetings that included an anti-union video and sent home union activists to prevent them from speaking to fellow employees – all allegedly in violation of federal labor law. Attorneys for the union said they plan to file a complaint with the National Labor Relations Board this week.

Albertsons said that all actions it has taken have been in compliance with the law.