He replaces Andy Clarke on July 11

BENTONVILLE, Ark. — Walmart has tapped the leader of its China unit, Sean Clarke, to replace Andy Clarke as chief executive officer of Asda Group PLC in the United Kingdom.

Sean Clarke

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

Sean Clark, who started his retail career at Asda in 2001, will attempt to stem the decline in sales and market share at the supermarket chain.

Profit margins at Britain’s “big four” grocery chains — Asda, Tesco PLC, J. Sainsbury PLC and Wm Morrison — hit historic lows after the retailers slashed prices to do battle with German discounters Aldi and Lidl. Expansion of the discounters cost Asda its status as the U.K.’s cheapest mainstream grocer.

Sean Clarke is slated to take over at Asda on July 11, Walmart said. His deputy CEO will be Roger Burnley, who is due 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.”

Walmart said Andy Clarke, who has been at Asda for more than two decades, will serve as an adviser to the company through the end of the year.