An estimated 18,000 Costco employees are members of the International Brotherhood of Teamsters, and 85% of them voted to strike.

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.

Costco Teamsters have voted to authorize a strike. The vote, passed with 85% of voters in favor, acts as a push from union members for a fair contract offer as the Costco Teamsters National Master Agreement is set to expire on Jan. 31.