ST. LOUIS -- While calling their workers "the best at what they do," the St. Louis area's three largest supermarket chains on Thursday began looking for temporary replacements in case of a walkout early next week.

Schnuck Markets Inc., Dierbergs Markets Inc. and Shop 'n Save Warehouse Foods Inc. -- which make up The Greater St. Louis Food Employers Council -- placed a full page ad in the main section of the St. Louis Post-Dispatch's Thursday editions seeking temporary cashiers and clerks.

The ad, published two days after union workers at the stores rejected a nearly four-year contract proposal that supermarket officials have called their final offer, told consumers the makeshift hiring is a "precautionary measure and does not mean a strike or lockout will occur."

"Our companies must now accelerate our efforts to hire and train replacements in order to continue serving our customers," the ad says.

St. Louis has never had a grocery workers strike.

Ed Finkelstein, spokesman for United Food and Commercial Workers Union Local 655, said he was not surprised by the move. However, he said it was a "farce" to believe the stores could adequately train replacement workers in three days.

In a statement Thursday, the union said customers could expect "a quagmire at the checkout lines."

"Service throughout the store will be in chaos," it said. "Customers can expect long waits in line and emptying shelves."

Full-time temporary workers will be paid $12.50 an hour, an amount a clerk with nearly five years of experience could earn under the proposed contract. Temporary workers hired part-time would earn $10 an hour, compared to $7 an hour for their union counterparts.

The decision whether to strike comes Tuesday morning, when Local 655 members are to gather at the America's Center convention center in downtown St. Louis. A two-thirds majority of those in attendance is required to authorize a strike.

About 5,600 of Local 655's 10,200 members voted on the contract proposal, with 64 percent opposed. If the strike vote fails, the contract takes effect.

Supermarket officials have said they hope to avert a strike, but must remain prepared to serve customers in case of a walkout at the 94 grocery stores and four related businesses.

The ad ensures customers that the stores will not compromise quality, service and value and will continue attempts to avoid a work stoppage.

"Our associates are the best at what they do and deserve the best wages and benefits," the ad says. "The Council members' contract offer is the best in St. Louis and among the best in the Midwest."

The proposal would have required workers to assume a greater share of medical bill costs through higher deductibles and co-payments for some services. It also offered a raise of 75 cents an hour, with 25-cent raises in the second, third and fourth years, plus a 20-cent-an-hour bonus if the union ratified the agreement. The raise only applied to workers who make $9 or more an hour. Union members said baggers would receive a raise of a nickel an hour.

The contract included two additional vacation days and more full-time jobs for workers at the grocery store chains.

The possible strike would not apply to stores outside the St. Louis area, including 14 Shop 'n Save stores and 21 Schnucks locations in Illinois, five Schnucks stores in Indiana and three Schnucks supermarkets in Jefferson City, Columbia and Cape Girardeau. It also would not affect 16 Logli stores operated by Schnucks in Illinois, Wisconsin, Tennessee and Mississippi.