* Copper up 0.2 percent on both LME and ShFE. * Copper on track to post biggest monthly fall since May 2010 * Grasberg strike threat, lower Chile copper output supports * Coming Up: U.S. Factory orders/durable goods Jul; 1400 GMT (Updates prices, adds quotes and details) By Carrie Ho SHANGHAI, Aug 31 (Reuters) - Copper edged up on Wednesday, supported by a strike threat at the Grasberg copper mine in Indonesia and news of lower output from Chile in July, but gains were reined in by weak economic data that fanned fears of a global economic slowdown. Copper prices, in both London and Shanghai, were headed for their biggest monthly drop in 15 months. Three-month copper on the London Metal Exchange edged up 0.2 percent to $9,180.25 a tonne by 0711 GMT, after rising 0.9 percent in the previous session. It is on track for a monthly fall of 6.4 percent, its largest since May 2010. The most-active November copper contract on the Shanghai Futures Exchange SCFc3 closed 0.2 percent higher at 68,360 yuan per tonne, after rising 0.9 percent in the previous session. It was down 5.9 percent for the month, also its biggest drop since May 2010. "I think copper has been in a technical rebound this week boosted by the strike threat in Indonesia and anticipation of China restocking soon," said Minmetals Futures analyst Zhuo Gui Qiu. Workers at Freeport-McMoRan Copper & Gold's Grasberg mine in Indonesia plan to stage a strike after talks with the company failed to resolve a pay dispute, in a move that could tighten global copper supplies and lift prices. Copper prices were also underpinned by a drop in output from Chile, which provides around a third of the world's copper. Chile produced 373,498 tonnes of the metal in July, down 18 percent from the same month last year, the government said on Tuesday. "Some renewed talk of U.S. embarking on a QE3 and the paring of losses of Shanghai equities in later trading also helped boost sentiment," the Minmetals analyst added. The U.S. Federal Reserve could embark on a third round of quantitative easing (QE) depending on upcoming economic data but should first confirm that inflation has eased, a senior Fed official said in Japan's Asahi newspaper on Wednesday. President Barack Obama said on Tuesday there was a range of policy options available that could create up to a million new U.S. jobs, in remarks ahead of a major economic speech he will deliver next week. The U.S. central bank in early August discussed a range of unusual tools it could use to help the economy, with some officials pressing for bold new steps to shore up a flagging recovery, minutes revealed. "In China, investors have been buying on dips for over a week now, which lends support to prices," said a Shanghai-based trader. But a slew of weak economic data, from the United States, the euro zone and Japan, weighed on market sentiment. U.S. consumer confidence plunged in August to its lowest since the 2007-2009 recession, after a bruising battle over the U.S. budget slammed stock prices and pushed the nation to the brink of default. Euro zone economic sentiment fell more than expected in August, underlining prospects for slower economic growth and expectations that the European Central Bank may cut inflation forecasts and cease raising interest rates. In Japan, industrial output rose a weaker-than-expected 0.6 percent in July, government data showed on Wednesday, in a sign that recovery from the March earthquake is losing steam as a surging yen and slowing global demand cloud the outlook. Base metals prices at 0711 GMT Metal Last Change Pct Move YTD pct chg LME Cu 9180.25 20.25 +0.22 -4.37 SHFE CU FUT NOV1 68360 110 +0.16 -4.86 LME Alum 2440.00 15.00 +0.62 -1.21 SHFE AL FUT NOV1 17470 25 +0.14 3.74 HG COPPER SEP1 415.15 2.60 +0.69 -6.49 LME Zinc 2282.00 -3.00 -0.13 -7.01 SHFE ZN FUT NOV1 17360 45 +0.26 -10.86 LME Nickel 21947.00 -3.00 -0.01 -11.33 LME Lead 2567.00 9.00 +0.35 0.67 SHFE PB FUT 16955 50 +0.30 -7.60 LME Tin 24025.00 25.00 +0.10 -10.69 LME/Shanghai arb 148 Shanghai and COMEX contracts show most active months ^ LME 3-m copper in yuan, including 17 pct VAT, minus SHFE third month

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