UPDATE 1-UK supermarket Asda promotes Roger Burnley to top job

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LONDON, Oct 30 (Reuters) - Asda, the British supermarket arm of U.S. retailer Walmart, said on Monday Sean Clarke would step down as president and chief executive on Jan. 1 next year and be succeeded by his lieutenant Roger Burnley.

Burnley, a former Sainsbury's executive, joined Asda as chief operating officer and deputy CEO in October 2016, three months after Clarke moved from Wal-Mart China to lead the UK business.

Roger was purposefully brought back to Asda to partner with Sean ahead of the transition to Roger taking up the position of CEO," said Dave Cheesewright, CEO of Walmart International.

"He and Sean have worked as a great team and Im really confident in Rogers ability to continue building upon our returning momentum," he said.

Of Britain's big four supermarket players - market leader Tesco, Sainsburys, Asda and Morrisons -- Asda has been hurt the most by the rise of German discounters Aldi and Lidl as its traditional price advantage was eroded.

However, in August Asda reported its first underlying sales growth in three years and said its back-to-basics turnaround plan was working. (Reporting by James Davey; editing by Costas Pitas and Kate Holton)