U.S. clothing company Gap has announced plans to triple the number of its stores in China by the end of next year.

The San Francisco-based clothing chain said Thursday it will open about 15 stores by the end of this year and plans to have a total of 45 by the end of fiscal year 2012.

The company has been struggling with tough competition and sluggish sales in the U.S. and is looking to expand its markets overseas.

Gap says it is also launching its first overseas Old Navy store in Japan in the next 18 months.

The company, which operates Gap, Banana Republic and Old Navy clothes stores, also said it is working on strategies to improve sales in North America. The strategies will include reducing the number of Gap stores to 700 from about 900, improving the floor display and introducing more color and patterns to clothing.