* Rusal cuts aluminium output by 357,000 T * Tin exports from Indonesia drop to 11-mth low in July By Harpreet Bhal LONDON, Aug 19 (Reuters) - Copper prices slipped on Monday, hit by uncertainty about when the U.S. Federal Reserve could ease back on stimulus that has helped fuel gains in commodities in recent years. Three-month copper on the London Metal Exchange traded at $7,345 a tonne at 0924 GMT, down from a close of $7,400 on Friday. The metal used in power and construction gained 1.7 percent last week, its third straight weekly gain, and has recovered more than 11 percent from three-year lows plumbed in late June. Prices, however, are still more than 7 percent lower in the year to date. The Fed publishes the minutes of its July 30-31 meeting on Wednesday, and uncertainty remains over the pace and timing of plans to trim its bond-buying programme. The ultra-loose monetary policy adopted by central banks around the world in the last few years has drawn investors to commodities as an alternative to interest-bearing assets. "The base metals market has recently experienced a short squeeze, catalysed by strong Chinese export data, that has seen participants that were short look to cover their positions," said George Adcock, senior metals and macro analyst at Marex. Traders will look for a continuation of recent strength in data from China when the HSBC Chinese flash manufacturing PMI is released on Tuesday, Adcock said. "If this is the case, and the short-covering is to continue, our favoured metals, in terms of positioning, would be nickel and copper," he added. Copper prices have found support ahead of a seasonally stronger period for demand in top consumer China, but growth concerns are likely to resurface and curb potential gains, said analyst Tim Radford at Sydney-based adviser Rivkin. "The key thing that is really driving the copper market is a weaker dollar ... If we see the USD weakness end then that will weigh on commodity markets - copper is probably due for a pull back," he added. The dollar held steady against a basket of currencies. A stronger dollar makes commodities priced in the U.S. unit more expensive for holders of other currencies. U.S. hedge funds and money managers sharply added bullish bets in copper futures and options, switching the market into its first net longs since February, data showed. Investors are likely to focus on results from mining firms this week, with Glencore Xstrata expected to write down the value of assets inherited from Xstrata by as much as $7 billion when it reports first-half earnings on Tuesday. BHP Billiton will also report on Tuesday. Rusal, the world's largest aluminium producer, said it would cut aluminium output by 357,000 tonnes, or around 8.5 percent of production, more than previously planned cuts of 7 percent. In Indonesia, refined tin shipments from the world's top exporter dropped to an 11-month low in July, with uncertainty over a series of new regulations likely to crimp overseas sales further in the next few months. Metal Prices at 0926 GMT Comex copper in cents/lb, LME prices in $/T and SHFE prices in yuan/T Metal Last Change Pct Move End 2012 Ytd Pct move LME Alum 1948.00 3.00 +0.15 2073.00 -6.03 LME Cu 7344.25 -55.75 -0.75 7931.00 -7.40 LME Lead 2252.50 3.00 +0.13 2330.00 -3.33 LME Nickel 14891.00 166.00 +1.13 17060.00 -12.71 LME Tin 21815.00 -110.00 -0.50 23400.00 -6.77 LME Zinc 2004.75 -3.25 -0.16 2080.00 -3.62 SHFE Alu 14510.00 35.00 +0.24 15435.00 -5.99 SHFE Cu* 52870.00 -10.00 -0.02 57690.00 -8.36 SHFE Zin 15195.00 85.00 +0.56 15625.00 -2.75 ** Benchmark month for COMEX copper * 3rd contract month for SHFE AL, CU and ZN SHFE ZN began trading on 26/3/07

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