Lawson Inc., the nation's second-biggest convenience store operator, is looking to buy chains in the U.S. as it speeds up overseas expansion with the aim of boosting its number of overseas outlets by about a quarter within a year.

"In the U.S., where the market is mature, mergers and acquisitions are a simple and straightforward way for us to expand, which would also allow us to buy time to boost the number of shops," Sadanobu Takemasu, who became Lawson president and chief operating officer Wednesday, said in an interview.

Lawson is not working on any deals at the moment, although it could take place any time given the opportunity, according to the 46-year-old, who said he will also focus on expanding in Southeast Asia. The company, which operates about 12,500 stores in Japan and 793 outside the country, is targeting a 26 percent increase to 1,000 overseas shops by February 2017.