More than 1,000 unionized Starbucks workers are on strike Thursday at 65 U.S. stores. The strike has closed some stores on Starbucks’ Red Cup Day, which is typically one of the company’s busiest days of the year. Starbucks gives away free, reusable cups on that day to customers who buy a holiday drink. The union working to organize Starbucks baristas says the striking workers are protesting a lack of progress in labor negotiations with the company. The two sides haven't been at the bargaining table since the spring. Starbucks Workers United says the walkout will impact stores in 45 cities, including New York, Philadelphia, Minneapolis and Dallas. Starbucks says fewer than 4% of its U.S. stores are unionized, and most stores will be operating normally.