BENTONVILLE, Ark. — Sean Clarke, who has led Walmart’s China business, will replace Andy Clarke as chief executive officer of Asda Group PLC in the United Kingdom.

“Andy Clarke has decided the timing is right to step aside from his role with the company,” Walmart announced in a statement. “Sean’s leadership will allow Asda to build upon the momentum of project renewal and reposition the business in a very competitive marketplace.”

Sean Clark began his retail career at Asda in 2001. In his new position, he will attempt to stem the decline in sales and market share at the supermarket chain.

Profit margins at Britain’s major grocery chains — led by Asda, Tesco, J. Sainsbury and Wm Morrison Supermarkets — hit historic lows after the retailers slashed prices to do battle with German discounters Aldi and Lidl.

Sean Clarke is scheduled to take over at Asda on July 11, Walmart said. His deputy CEO will be Roger Burnley, who is expected to join Asda from Sainsbury in October. “Rejoining Asda at such a critical point in the development of the U.K. retail market is both a challenge and a privilege,” said Sean Clarke. “After spending the last 15 years in Walmart’s global retail markets, I’m looking forward to returning to the business that got me hooked on grocery ­retail.”

Andy Clarke will serve as an adviser to the company through the end of the year.