Coordinated strikes ahead of Christmas in a handful of cities including San Francisco and New York see the Teamsters challenge the nation’s second-largest private employer.

Workers at an Amazon warehouse in San Francisco are on strike Thursday, joining six other delivery stations of the e-commerce company across the country. The Teamsters, who are seeking a labor agreement during a key shopping period,

The International Brotherhood of Teamsters said workers at seven Amazon facilities across the U.S. will begin a strike Thursday morning.