* LME copper heads for 2nd monthly gain, up 13 pct Jan-Feb * ECB to inject more liquidity into financial system * Coming Up: U.S. GDP, 1330 GMT (Recasts lead, updates prices) By Manolo Serapio Jr SINGAPORE, Feb 29 (Reuters) - London copper rose marginally to extend gains to a fourth day on Wednesday, helped by fresh efforts by the European Central Bank to inject more cash to ease the region's debt strains and another upbeat piece of U.S. economic data. Despite unimpressive demand from top consumer China, copper has gained more than 13 percent so far this year, with the euro zone debt crisis being slowly resolved and the U.S. economy showing a more sustained path to recovery. Three-month copper on the London Metal Exchange edged up 0.2 percent to $8,615.25 a tonne by 0707 GMT, reversing early losses. The metal is on course for a second month of gains in February after hitting a five-month top of $8,765 early in the month. The most-traded May copper contract on the Shanghai Futures Exchange was little changed at 61,070 yuan ($9,700) a tonne at the close. Investors were squaring positions on the last day of the month, said Ker Chung Yang, analyst at Phillip Futures. "We are seeing a consolidation, but the market looks like it can still go higher later in the day with the ECB injection. The upside is likely to be capped at $8,800," he said. The European Central Bank is expected to pump half a trillion euros into the euro zone's troubled financial system for the second time in as many months later in the day in what it hopes will be the last such operation to fight the euro zone crisis. A recovering jobs market helped lift U.S. consumer confidence to a one-year high this month, helping the Dow close above 13,000 for the first time since May 2008. But analysts say Chinese copper demand, which comprises 40 percent of the global market, needs to bounce back, and strongly, to justify the metal moving higher. Soft physical premiums for copper in Shanghai reflect continued weakness in Chinese demand, with a Shanghai-based trader saying premiums for cash copper have slipped to $40 to $70 per tonne over London prices from around $80 to $90 earlier this month. Stockpiles of copper at warehouses monitored by the Shanghai Futures Exchange CU-STX-SGH dropped last week for the first time since early December, but at more than 216,000 tonnes, stayed well near 10-year highs. In contrast, LME copper inventories are below 300,000 tonnes, at their lowest since August 2009. The release of a key Chinese economic indicator on Thursday may help investors decipher the country's demand ahead. China's official purchasing managers' index, which measures activities in the domestic manufacturing sector, is forecast to rise to a five-month high in February, according to a Reuters poll. Base metals prices at 0707 GMT Metal Last Change Pct Move YTD pct chg LME Cu 8615.25 15.25 +0.18 13.36 SHFE CU FUT MAY2 61070 10 +0.02 10.31 HG COPPER MAR2 391.70 0.50 +0.13 14.00 LME Alum 2333.00 8.00 +0.34 15.50 SHFE AL FUT MAY2 16250 -20 -0.12 2.56 LME Zinc 2116.25 -6.75 -0.32 14.70 SHFE ZN FUT MAY2 16140 15 +0.09 9.09 LME Nickel 20025.00 270.00 +1.37 7.03 LME Lead 2244.00 -11.00 -0.49 10.27 SHFE PB FUT 16315.00 5.00 +0.03 6.74 LME Tin 24195.00 140.00 +0.58 26.02 LME/Shanghai arb^ 2374 Shanghai and COMEX contracts show most active months ^ LME 3-month copper in yuan, including 17 pct VAT, minus SHFE third month ($1=6.2990 Chinese yuan) (Reporting by Manolo Serapio Jr.; Editing by Sugita Katyal)

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