Britain's top share index was 0.1 percent lower by mid-session Thursday, weighed on by weaker commodity stocks as metal prices fell, ahead of results from U.S. banks Citigroup (C.N) and Goldman Sachs (GS.N).

At 1044 GMT, the FTSE 100 .FTSE was down 5.56 points at 5,250.54, retreating from a 56-week closing high on Wednesday.

Miners were the top fallers as profit takers moved in as metal prices retreated.

Rio Tinto (RIO.L), Xstrata (XTA.L), Lonmin (LMI.L), Anglo American (AAL.L) and Fresnillo (FRES.L) fell 1.1-1.9 percent.

It's a little bit of a sell-off from the last few days. The FTSE's had a phenomenal run. All eyes will be on the numbers coming from the U.S. later, said Mark Priest, senior trader at ETX Capital.

Anglo American (AAL.L) was the biggest faller, down 3.4 percent, after rival Xstrata (XTA.L) said it would not make a formal takeover offer. 

Xstrata fell 1.9 percent, with Lonmin (LMI.L), Eurasian Natural Resources (ENRC.L), Fresnillo (FRES.L) and Kazakhmys (KAZ.L) off 0.7-1.9 percent.

Energy stocks were lower as investors banked profits following the preious session's gains and as crude CLc1 slipped back towards $75 a barrel.

BG Group (BG.L), Royal Dutch Shell (RDSa.L), BP (BP.L) and Cairn Energy (CNE.L) shed 0.3-2.2 percent.

Tullow Oil (TLW.L), which said in a drilling update the Mahogany-4 well had found oil, also retreated, dropping 1.1 percent.

U.S. BANKS EYED

The index rose 2 percent on Wednesday after upbeat quarterly earnings from U.S. investment bank JPMorgan Chase (JPM.N), which followed U.S. chipmaker Intel's (INTC.O) forecast-beating results on Tuesday.

Bank stocks were mixed ahead of results from Citigroup and Goldman Sachs, due at 1130 GMT and 1200 GMT respectively.

Heavyweight HSBC (HSBA.L), Barclays (BARC.L) and Standard Chartered (STAN.L) lost 0.6-1 percent, while Royal Bank of Scotland (RBS.L) and Lloyds Banking Group (LLOY.L) added 1 percent and 0.5 percent respectively.

The FTSE 100 has surged more than 51 percent from a six-year trough in March, but is still 3.3 percent below its level in mid-September 2008 before the collapse of Lehman Brothers.

British blue-chips underperformed the FTSE Eurofirst 300 .FTEU3, which added 0.5 percent on Thursday.

The miners are fairly dominant in the FTSE as opposed to other indices, which is probably why the UK index is underperforming at the moment, said Priest at ETX Capital.

Food retailer J Sainsbury (SBRY.L) comfortably topped the FTSE risers chart, up 8.6 percent with traders citing talk of a bid from Qatar.

The news helped saw peers Tesco (TSCO.L) and Wm Morrison Supermaket (MRW.L) both rise around 2 percent.

Life Insurers were also in demand after Nomura issued a bullish note on the sector.

Aviva (AV.L), Prudential (PRU.L) and Legal & General (LGEN.L), which were the broker's top European picks, rose 0.8-1.8 percent, while Friends Provident (FP.L), Old Mutual (OML.L) and Standard Life (SL.L) climbed 0.1-0.7 percent.

Among individual movers, Burberry (BRBY.L) hit a 22-month high, rising 1 percent and extending the previous session's gains, as JPMorgan raised its target price on the luxury goods group and lifted its full-year forecasts, following a first-half trading update on Wednesday.