Dec 24 (Reuters) - A strike at Starbucks' ( SBUX ) U.S.

stores will expand to over 300 stores on Tuesday, with more than

5,000 workers expected to walk off the job, before the five-day

work stoppage ends later on Christmas Eve, the workers' union

said.

Starbucks Workers United, representing employees at 525

stores nationwide, said more than 60 U.S. stores across 12 major

cities, including New York, Los Angeles, Boston and Seattle,

were shut on Monday.

Talks between Starbucks ( SBUX ) and the union had hit an impasse

with unresolved issues over wages, staffing and schedules,

leading to the strike.

The Christmas Eve strike on Tuesday was projected to be the

largest ever at the coffee chain, the union added.

Starbucks ( SBUX ) did not immediately respond to a Reuters request

for comment outside regular business hours.

"These strikes are an initial show of strength, and we're

just getting started," an Oregon barista said in a union

statement.

The Seattle-headquartered firm has previously said it was

ready to continue negotiations, claiming the union delegates

prematurely ended the bargaining session.

Earlier this month, the workers' group rejected an offer of

no immediate wage hike and a guarantee of a 1.5% pay increase in

future years.

The union also said that Starbucks ( SBUX ) has yet to present its

workers with "a serious economic proposal."

(Reporting by Bipasha Dey, Shubham Kalia and Gursimran Kaur in

Bengaluru; Editing by Abinaya Vijayaraghavan)