MELBOURNE, April 13 (Reuters) - London aluminium slipped on Friday but was on track for its biggest weekly gain on record after the United States imposed sanctions on Russia's UC Rusal, the world's second biggest producer of the metal, raising supply concerns. Traders have this week scrambled to stockpile aluminium, given customers who can no longer take Rusal metal will have to find a fresh source of supply in what is an already fast-tightening market. After a decade of oversupply, the global aluminium market has facing a deficit of some 800,000 tonnes already this year, said Dominic Schnider of UBS in Singapore. "We have a bullish view on aluminium with $2,400 as a target in three months. That's really based on the perception that overall supply growth is constrained by China and they have genuine interest in keeping an eye on capacity," Schnider said. FUNDAMENTALS * London Metal Exchange aluminium fell by 1.6 percent to $2,287.50, trimming gains for the week that were still approaching 14 percent. Prices topped out at $2,325 a tonne on Thursday which was a six-year high. A trader noted very wide spreads, reflecting an unusual lack of liquidity in the LME's biggest contract. * RUSAL: U.S. sanctions on Russian businesses and individuals are hitting companies, including aluminium giant Rusal controlled by tycoon Oleg Deripaska, and triggering responses across markets. * US ALUMINIUM STOCKS: Almost all the aluminium in the United States was removed from Comex warehouses this week. Stocks tumbled by about 44,000 tonnes to 11,168 tonnes. AL-TTLTTDY-STX * SCRAMBLE: The rush for stocks was also reflected in time spreads on the LME with soaring prices for cash aluminium against the benchmark three-month contract. Cash aluminium traded $52 against three months, the highest in more than a decade. CMAL0-3 * CHINA ALUMINIUM: China's aluminium exports in March rose to their highest since June as favourable pricing led the world's biggest producer to sell more abroad even as the nation faces scrutiny over its trade practices. * CHINA EXPORTS: China's exports growth overall unexpectedly fell in March, the first drop since February last year. * COPPER: LME copper edged up by 0.1 percent to $6,828.50 a tonne by 0730 GMT, following a 1.9 percent drop from the previous session. Prices have support at the 200-day moving average of $6,743. Shanghai Futures Exchange copper eased by 0.7 percent. * POLLUTION: In what could potentially help U.S. aluminium makers boost production more quickly, U.S. President Donald Trump on Thursday ordered the Environmental Protection Agency to speed up its decision-making on air quality permitting to make it easier for manufacturers to expand and open new plants. * OTHER METALS: Both Shfe aluminium and nickel closed nearly 2 percent higher in volatile trade, while Shfe zinc closed nearly 2 percent down, on talks of China's state reserves selling metal.