Britain's FTSE edges down as investors await May's Brexit speech

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* FTSE 100 down 0.1 pct

* North Korea's bomb threat weigh on markets

* Financials, miners suffer

* May's speech in Florence could impact sterling

By Julien Ponthus

LONDON, Sept 22 (Reuters) - UK shares opened lower on Friday after North Korea's threat to test a hydrogen bomb over the Pacific ocean weighed on markets globally and as investors await Prime Minister Theresa May's speech on Brexit later in the afternoon.

The blue chip FTSE 100 index was down 0.1 percent at 7,255 points by 08h18 GMT, broadly in line with the rest of European bourses, where financials and mining stocks suffered from geopolitical tensions.

Shares (Berlin: DI6.BE - news) in miners BHP Billiton (NYSE: BBL - news) , Antofagasta (Other OTC: ANFGF - news) , Angloamerican, Glencore (Frankfurt: 8GC.F - news) lost between 1.7 and 2.2 percent as metals prices fell with investors slashing risk amid escalating tensions on the Korean peninsula and ongoing jitters about China debt after a ratings downgrade.

Rio Tinto (Hanover: CRA1.HA - news) , which said it would buy back an additional $2.5 billion worth of its shares, lost 0.7 percent.

British banks also weighed on the index, with Lloyds , HSBC and Barclays (LSE: BARC.L - news) and Royal Bank of Scotland RBS.L all up between 0.4 and 0.8 percent.

At the center of traders attention was May's attempt this afternoon to rescue stalled Brexit talks with a speech in the Italian city of Florence, where she will seek to convince the European Union she is ready to cut a fair divorce deal.

"If the markets like what they hear and there isn't a negative response from the EU then the recent rally in the pound could extend further", said Michael Hewson, chief market analyst at CMC Markets (LSE: CMCX.L - news) .

Britain's FTSE's companies earn mainly in foreign currencies and have suffered from the recent rise in the pound, due notably to a likely interest rate hike by the Bank of England in the coming months.

Many British corporate have enjoyed an accounting boost as their revenues were converted back to the British currency following its plunge after the Brexit vote last year.

On the corporate front, Smiths Group (Frankfurt: QS2A.F - news) was the worst performer of the FTSE, down about 4 percent pct after slowness at its two biggest businesses John Crane and Smith Medical weighed on revenue growth.

Easyjet (Frankfurt: A1JTC1 - news) was among the stocks in positive territory with a 1.2 percent rise after Air Berlin (LSE: 0GPE.L - news) 's creditors picked the low-cost airline and German flagship carrier Lufthansa (Xetra: LHAB.DE - news) as possible buyers for the insolvent carrier's aviation business. (Reporting by Julien Ponthus Editing by Jeremy Gaunt)