* Copper touches lowest level since May 3 * Aluminium inventories rise to new record * Coming up: Fed policy statement at 1800 GMT By Susan Thomas and Eric Onstad LONDON, June 19 (Reuters) - Copper slid on Wednesday to its lowest in over six weeks, the third straight day of losses, as investors worried about the potential for less stimulus from the U.S. Federal Reserve ahead of the conclusion of its two-day policy meeting. Speculation that the central bank will start tapering its asset-buying programme before the end of the year has triggered a sell-off in financial markets, although on Wednesday some markets were fairly steady ahead of the policy statement at 1800 GMT. Most economists do not expect the Fed to immediately scale back purchases from its current $85 billion monthly pace. Three-month copper on the London Metal Exchange shed 0.86 percent to $6,945 a tonne by 1439 GMT, after touching a session low of $6,925, its lowest since May 3. "We suspect that should the Fed indicate it is moving towards some tapering...the dollar should strengthen, in theory weakening base metals further," said analyst Edward Meir at INTL FCStone in New York. Many fundamental issues, however, should support the price. "But even though we could have some big news from a macro perspective, when you look at it on a micro perspective things are actually looking okay for copper," Barclays analyst Gayle Berry said. The world's second-largest copper mine, Freeport McMoRan Copper and Gold Inc's Grasberg in Indonesia, remains closed five weeks after a training tunnel collapse killed 28 workers. Also, a shortage of cash in top commodity consumer China is boosting imports of copper as a financing tool, resulting in premiums paid for spot refined metal supplies from overseas climbing to near four-year highs. On the other hand, inventories of copper in warehouses monitored by the LME have been climbing, which has contributed to the metal's almost 12 percent fall so far this year. Latest LME data showed stocks jumped by 6,174 tonnes, reminding investors of an expected surplus this year, although many analysts say the surplus is likely to be lower than they expected earlier this year because of production outages including Freeport's Grasberg mine. Aluminium inventories in LME-monitored warehouses have also surged this week, with data on Wednesday showing Detroit accepting almost 60,000 tonnes of the metal, setting a new record high for total stocks at 5.4 million tonnes. The climbing LME inventories is expected to hit makers of products such as cans and packaging foils, who face record high aluminium surcharges in the U.S. Midwest, industry sources said. Benchmark three-month aluminium lost 0.8 percent to $1,827 a tonne, the weakest since May 15. "Two days of consecutive closes below $1838 will likely set the complex up for a retest of the May low of $1809," Meir said in a note. Metal Prices at 1443 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

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