The Workers United union has reportedly announced a strike involving thousands of employees at numerous Starbucks Corporation (SBUX  ) locations.

This walkout is planned for the coffee giant's highly anticipated Red Cup day, a key promotional event occurring this Thursday during the crucial holiday season, reported Reuters.

Starbucks traditionally offers free reusable holiday-themed cups with coffee purchases on Red Cup day.

The report noted Workers United has characterized Red Cup day as "one of the most infamously hard, understaffed days for the baristas" at Starbucks.

The union called for protests at more than 100 Starbucks stores at Red Cup day last year, as per the report.

In response to the planned walkout, Starbucks reportedly acknowledged awareness of the proposed action at a "small subset" of its U.S. stores. "Workers United hasn't agreed to meet to progress contract bargaining in more than four months and has yet to deliver on the campaign promises they've made," Starbucks told Reuters.

Workers United currently represents more than 360 unionized Starbucks stores and over 9,000 employees.

Price Action: SBUX shares traded higher by 1.16% at $104.71 on the last check Tuesday.