The British supermarket chain Sainsbury's says it has agreed to buy Walmart Inc.'s U.K. unit, Asda, for 7.3 billion pounds ($10.1 billion) in cash and stock in what would mark a seismic shift in the country's grocery market.

J Sainsbury plc, the chain's corporate name, says it will give Walmart 4.3 billion pounds worth of stock and 2.98 billion pounds in cash for Asda. Walmart will own 42 percent of the combined company.

The merger would create Britain's largest supermarket chain, with more than 30 percent of the market, putting it ahead of the current leader, Tesco. The deal would be subject to scrutiny by the Competition and Markets Authority.