The contract was set to expire last night.

“These next two weeks are critical,” said Mickey Kasparian, president of the union's Local 135, which covers San Diego and Imperial counties. “We have either got to hammer out a deal or make significant progress.”

The two sides also said a federal mediator has become involved in the talks and had requested the contract extension.

Adena Tessler, the spokeswoman for the region's three major grocery store chains, said the companies are committed to working with the union to come up with a mutually beneficial contract. While the supermarkets were willing to continue negotiations without an extension, the deal gives all involved peace of mind as the talks continue.

“The workers and the customers can be confident that it will be business as usual at the grocery store,” Tessler said.

The current labor deal helped end a bitter 4 ½-month strike and lockout in 2004 but little progress has been made on a new contract. The grocery chains – Albertsons, Ralphs and Vons – and the United Food and Commercial Workers union typically renegotiate a deal every three years.

The current contract affects about 65,000 workers at almost 800 stores throughout Southern California. The three chains account for more than 50 percent of the grocery business in the region.

Ruth Milkman, a sociology professor who directs the Institute of Industrial Relations at the University of California Los Angeles, said the extension is good news for the union and its workers, but much work remains.

“Everything depends on how serious they are about having good-faith negotiations,” she said, adding that the involvement of federal mediator Linda Gonzalez is a hopeful sign.

Part of the deal stipulates that grocery workers at the three chains continue to work under the current contract with no work stoppages until March 19. Any wage increases under the new deal will be retroactive to March 5 as long as there is no strike or lockout.

While the two sides have agreed to an extension, they are still far apart on many issues, including wage increases and health care benefits for employees and retirees. Besides those issues, the union said it is set on eliminating a two-tier employee system that its members agreed to in the current contract.

Under that system, new hires get paid less than longtime employees, and it takes them longer to qualify for benefits. They also pay a greater share of the cost for those benefits.

The union has complained that the two-tier system is unfair because workers doing the same job get different pay. They blame it for increased employee turnover within the grocery industry as well as for the rising number of employees without health coverage.

The grocery stores chains, however, have said the two-tier system has been a success, helping trim costs and improve profits.

With the two sides so far apart on those issues, Milkman said, it is unlikely that the current extension will be enough time to resolve all the differences.

“It's a real question if two weeks is enough,” she said. “I predict there will be further extensions.”