The unionized Costco workers are on a contract that expires Jan. 31, according to their Teamsters representatives.

Members of the Teamsters union have authorized a strike against Costco on February 1 unless they reach a deal with the warehouse retailer before the current contract expires 31.

Thousand of Costco Teamsters across the U.S. are preparing to strike by the end of the month if the company does not present a "fair contract offer," the union says.