The general counsel of the NLRB determined that the coffee chain violated labor law by refusing to participate in collective bargaining sessions if some workers were present via videoconference, the report said.

"Now that it's clear we have the right to bargain using a virtual component, we hope Starbucks is ready, too," Tyler Keeling, a Starbucks' union leader from California said in a statement.

The development comes ahead of Starbucks interim CEO Howard Schultz's testimony before the U.S. Senate Health, Education, Labor and Pensions Committee on March 29, after earlier resisting requests to appear and answer questions about the company's compliance with labor law.

"Hearing this days before Howard Schultz is set to testify in front of the HELP committee is huge, especially because he has personally talked about the fact that Starbucks is refusing to bargain with us because of the Zoom screen," Keeling said.

Starbucks and the NLRB did not immediately respond to Reuters request for comment.

Employees at more than 280 out of Starbucks' roughly 9,000 company-operated U.S. locations have voted to join a labor union since 2021. The union is seeking better pay and benefits, improved health and safety conditions and protections against unfair dismissal and discipline.

(Reporting by Baranjot Kaur in Bengaluru; Additional reporting by Chandni Shah; Editing by Varun H K)