* U.S. spending cuts seen hurting growth * Chile's Escondida strike enters 13th day * Coming up: U.S. ADP employment June at 1215 GMT By Harpreet Bhal LONDON, Aug 3 (Reuters) - Copper fell to a three-week low on Wednesday on growing concerns that efforts by the United States to cut spending will hinder growth in the world's largest economy and hurt demand for metals, but supply uncertainty helped limit further falls as a strike at Chile's Escondida mine entered its 13th day. Benchmark copper on the London Metal Exchange fell to a low of $9,573 a tonne, its lowest level since mid July, and was at $9,580 by 1046 GMT, down 1.1 percent from a close of $9,680 a tonne on Tuesday. Agreement by lawmakers on a last-gasp deal to raise the U.S. borrowing capacity and avoid a debt default failed to bring much relief as investors focused on the implications of tighter fiscal policy on U.S. growth. Data earlier in the week showed U.S. manufacturing grew at its slowest pace in two years in July, raising fears over the pace of recovery in the world's largest economy and prompting concerns about demand for base metals. "The recent disappointing economic numbers from the U.S. are weighing on prices and risk aversion is high among market players. Economic data will be closely watched this week," said Daniel Briesemann, analyst at Commerzbank. U.S. non-farm payrolls data, used as a key gauge of economic health and due on Friday, is expected to show its economy added 85,000 jobs in July after growing by just 18,000 in the previous month. Supply concerns, however, helped limit further falls in copper as negotiations between union officials and Chile's Escondida mine owner BHP Billiton stretched into a second day on Wednesday The strike at Escondida has stoked fears of contagion to other mines, fanning global supply fears, some analysts say. "Some in the copper industry fear that if BHP agrees to demands for a higher bonus at Escondida, workers at other mines in Chile could follow suit with similar demands," ANZ said in a note. Markets are closely watching developments in the euro zone debt crisis, with caution prevailing as five-year Italian bond yields reached the same level as Spain's, in a sign Rome is overtaking Madrid as a key focus of investors' concern about debt sustainability. Analysts at RBC said copper could break below the $9,600 a tonne mark in the short-term, with any weakness presenting a buying opportunity for investors. "Copper has seen a good support base around $9,600 for the past three weeks, but we think a test and break of that support line is inevitable in the short term. $9,000 is the next obvious line of support in the charts below that and we think any test of that level should be treated as a buying opportunity." CANCELLED WARRANTS DROP Reflecting soft demand for copper in the summer lull, cancelled warrants -- the metal earmarked for delivery -- at 2.8 percent of LME stocks of 465,850 tonnes are the lowest since mid April, and have been falling since June 22. "As positive as the market remains over the long run outlook for copper, the short-term picture has yet to improve with China's demand for the red metal still needing to improve beyond 2Q11 levels," VTB Capital said in a note. "Spot premiums will need to improve from current levels, with persistent inventory draws on the LME once China's bonded and SHFE warehouse stocks are nearly depleted." Aluminium fell to $2,560 tonne from $2,583. The metal has been helped by electricity supply concerns for smelters in China's Henan province. Some support for the metal also came from data on Tuesday showing U.S. auto sales edged higher in July Zinc , used in galvanising, slipped to $2,397 from $2,440, while battery material lead was at $2,541.50 a tonne from $2,561, hovering near its lowest since late June. Tin slipped to $26,800 from $27,250 and nickel fell to $24,075 from $24,800. Metal Prices at 1051 GMT Comex copper in cents/lb, LME prices in $/T and SHFE prices in yuan/T Metal Last Change Pct Move End 2010 Ytd Pct move COMEX Cu 435.90 -3.60 -0.82 444.70 -1.98 LME Alum 2583.00 -2.00 -0.08 2470.00 4.57 LME Cu 9679.00 -1.00 -0.01 9600.00 0.82 LME Lead 2560.00 -1.00 -0.04 2550.00 0.39 LME Nickel 24795.00 -5.00 -0.02 24750.00 0.18 LME Tin 0.00 -27250.00 -100.00 26900.00 -100.00 LME Zinc 2440.00 0.00 +0.00 2454.00 -0.57 SHFE Alu 18520.00 180.00 +0.98 16840.00 9.98 SHFE Cu* 72060.00 50.00 +0.07 71850.00 0.29 SHFE Zin 18395.00 -60.00 -0.33 19475.00 -5.55 ** Benchmark month for COMEX copper * 3rd contract month for SHFE AL, CU and ZN SHFE ZN began trading on 26/3/07 (Editing by Alison Birrane)

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