Britain's FTSE falls, set to snap three-week winning streak

(ADVISORY- Reuters plans to replace intra-day European and UK stock market reports with a Live Markets blog on Eikon - see cpurl://apps.cp./cms/?pageId=livemarkets for site in development. See the bottom of the report for more details)

* FTSE 100 poised to end three-week run of gains

* Weak copper prices hit mining stocks

* Burberry falls on slowdown at rival Kering (LSE: 0IIH.L - news)

* Sainsbury (Amsterdam: SJ6.AS - news) rises on rating upgrade

By Kit Rees

LONDON, April 22 (Reuters) - Britain's benchmark shares index fell on Friday as a drop in mining stocks and luxury goods group Burberry weighed on the market, which was heading towards its first weekly loss in a month.

The blue-chip FTSE 100 index was down 1.2 percent at 6,305.77 points, set to snap a three-week stretch of gains and slipping from a four-month high reached earlier in the week.

Mining stocks such as Anglo American (LSE: AAL.L - news) and Rio Tinto (LSE: RIO.L - news) were the worst performers, hit by a drop in copper prices.

Commodity prices have been under pressure throughout 2016 on concerns about a China-led global economic slowdown.

"Commodities have had a spectacular run over the past few months, but that doesn't really change the fundamental story," said IG (LSE: IGG.L - news) analyst Chris Beauchamp, who added that any future gains in the mining stocks look limited at the moment.

Burberry, meanwhile, fell by 1.7 percent after French peer Kering reported a slowdown in growth at its premium Gucci brand.

Supermarket chain Sainsbury, however, rose 1.5 percent after Deutsche Bank (LSE: 0H7D.L - news) raised its rating on the company to "buy" from "hold".

ADVISORY- Reuters plans to replace intra-day European and UK stock market reports with a Live Markets blog on Eikon (see cpurl://apps.cp./cms/?pageId=livemarkets for site in development). In a real-time, multimedia format from 0600 London time through the 1630 closing bell, it will include the best of our market reporting, Stocks Buzz service, Eikon graphics, Reuters pictures, eye-catching research and market zeitgeist. Breaking news and dramatic market moves will continue to be alerted to all clients and we will continue to provide a short opening story and comprehensive closing reports.

If you have any thoughts, suggestions or feedback on this, please email mike.dolan@thomsonreuters.com.

Mike Dolan, Markets Editor EMEA. (Additional reporting by Sudip Kar-Gupta; Editing by David Goodman)