"We want to empty those stores," said Doug Dority, international president of the United Food and Commercial Workers, on Tuesday. "We want to make sure these cash registers are empty."
Safeway, Albertsons Inc. and Kroger Co. are locked in the dispute with their Southern California workers over the cost of health care coverage and other issues.
Union leaders have said they consider Safeway the leader of the management side.
In some cases, the UFCW also planned to extend picket lines to Safeway stores outside the region in an attempt to keep employees from reporting to work, said UFCW national spokesman Greg Denier.
He declined to say when the boycott campaign would begin.
Safeway officials said they didn't expect the tactic to influence the dispute.
The unions' strategy was announced after 500 leaders and workers met for two hours behind closed doors at a hotel and then marched with thousands of other workers to a supermarket in Beverly Hills.
Clerks went on strike or were locked out Oct. 11 at nearly 860 Ralphs, Albertsons, Vons and Pavilions stores from San Diego to San Luis Obispo. Safeway owns the Vons and Pavilion chains.
Negotiations were scheduled to resume Friday for the first time in 10 days.
The UFCW said the chains had shaved $1.08 an hour off their proposed contribution to health care premiums.
The grocery companies countered they were no longer willing to absorb all the costs involved in maintaining health care benefits, saying they face pressure from Wal-Mart, Costco and other supermarket operators that don't pay as much toward employee benefits.