LONDON, June 9 (Reuters) - British supermarket group Sainsbury's SBRY.L is to trial selling clothing online, seeking to build on the success it has seen from a diversification into non-food products in its stores.

The firm, which trails market leader Tesco TSCO.L and is battling with Wal-Mart Stores' WMT.N Asda to be the UK's No. 2 grocer, said on Monday it will pilot selling its Tu clothing range over the Internet.

Sainsbury's began selling clothing in 1994 and last year over 7.5 million customers bought clothing items, generating sales of approximately 750 million pounds ($1.3 billion).

According to data from Kantar Worldpanel the firm is Britain's seventh largest clothing retailer by volume.

Sainsbury's said the pilot will begin in August with an invited group of customers in the Midlands, central England.

It will offer Tu womenswear, menswear and childrenswear clothing on a bespoke website. Customers can choose between 'Click & Collect' and home delivery services.

Orders will be fulfilled from Sainsbury's clothing depot in Bedford which serves the 400 stores selling its clothing.

The trial was announced ahead of a first quarter trading update on Wednesday.

After sustaining positive like-for-like sales for the best part of nine years, the grocer is expected to report a second successive negative quarter.

The update will be the last to be presented by Chief Executive Justin King.

After 10 years at the helm he will be succeeded by commercial director Mike Coupe following Sainsbury's annual shareholders' meeting on July 9. ($1 = 0.5956 British Pounds)

(Reporting by James Davey, Editing by Paul Sandle)

((james.davey@thomsonreuters.com)(+44 20 7542 7674)(Reuters Messaging: james.davey.thomsonreuters.com@reuters.net))

Keywords: J SAINSBURY CLOTHING/