Two supermarket chains in Arizona are preparing for a possible strike by advertising for temporary employees.

Fry's Food Stores, a subsidiary of Kroger, began running ads Saturday, The Arizona Republic reported. Safeway Arizona plans to do the same next week, a spokeswoman said.

A one-year extension of a contract that expired in 2008 ended Oct. 31. The United Food and Commercial Workers Union Local 99, which represents most of the stores' hourly workers at both chains, has set a strike deadline for 6 p.m. next Friday.

Jim McLaughlin, the head of the union, said his members make between $7.05 and $12.05 an hour.

"Some of our members haven't had a raise in six years," McLaughlin said.

A critical issue is a company demand that union members make contributions to their health plan. McLaughlin said they effectively do so now because of their low wages.