In what the union has dubbed "The Strike Before Christmas," more than 5,000 workers are walking out of 300-plus Starbucks locations nationwide Tuesday.

Starbucks' union says workers are walking off the job at some 300 — out of over 10,000 — stores across the U.S. as contract negotiations falter.

Workers in about 10 to 15 stores across the Los Angeles, Seattle and Chicago areas kicked off the strike, which spread to a similar number of stores in three additional metropolitan areas each day. By Monday, baristas in more than 50 stores in cities like Boston, Dallas, Denver, New York and Philadelphia did not report for work.