A rolling strike of Starbucks baristas began Friday and grows to include about 300 of the coffee giant's shops across the U.S.

Starbucks workers have expanded their strike to more cities and closed 59 stores across the U.S. as of Monday, the union said amid stalled negotiations.

Earlier, Starbucks said the union “prematurely ended” a bargaining session and called for talks to continue. The coffee chain has said it’s focused on improving workers’ experience and that baristas who work at least 20 hours a week receive $30 an hour, on average, when combining pay and benefits.