Japanese retail group Seven & i Holdings Co. said on Thursday it is considering acquisitions after reports that it was in talks to buy Marathon Petroleum Corp.’s Speedway gas stations for $22 billion.

Seven & I’s shares fell 8.8 percent.

The company, which runs the 7-Eleven convenience store chain, said in a statement it had not decided on any acquisitions. But it did not deny reports by Bloomberg and Nikkei that it was in exclusive talks to buy the Speedway business in the United States.

Bloomberg said a deal could be announced as soon as next week.

The news comes as the convenience store business, whose high margins and strong growth were the envy of the rest of Japan’s retail sector for years, faces market saturation, sluggish consumer spending and competition from Amazon.com.

The 7-Eleven chain has also been under pressure to review its 24-hour policy amid a tight labor market and analysts have said it makes sense for the company to focus more on the U.S. market.

Seven & i bought around 1,000 U.S.-based stores from Sunoco LP for $3.1 billion in 2018.

The convenience store business originated in the United States, but is now owned by the Japanese group, which also owns supermarket chain Ito-Yokado.