By Chloe Fussell LONDON (Reuters) - Copper and aluminium prices came under pressure on Monday as the market priced in lower demand from China and the United States ahead of key U.S. manufacturing data. Three-month copper on the London Metal Exchange was trading around $7,842 a tonne at 1112 GMT compared with $7,935 at the close on Friday, while aluminium was at $2,909 a tonne from $2,931. "Barring any supply-side event such as a strike or severe production disruptions, I see the market as steady towards the downside this week, as we're moving towards the seasonal slowdown in China," said Marc Elliott, analyst at investment bank Fairfax. Traders said a survey on manufacturing by the U.S. Institute for Supply Management due later on Monday could change or reinforce the weak outlook for copper as the United States is the world's second largest consumer Copper, used widely in the power and construction industries, has lost more than 20 percent since hitting a record high of $8,880 a tonne on April 17. The absence of Chinese consumers in the market and rising stocks have helped push prices down, analysts said. "The impact of slowing economic growth and rising inventories seems to be taking its toll on the entire complex, even though there appears to be a clear distinction between the three base metals that remain," BNP Paribas said in a note. Stocks of copper in LME warehouses fell 1,000 tonnes to 123,950 tonnes, but that is still more than 10 percent above the levels at the beginning of May. POWER Aluminium stocks at above 1,070,000 tonnes are about 60 percent above levels at the beginning of the year. But analysts expect concern about power supplies in China to support prices. Also in the long term, analysts say the outlook for energy-intensive aluminium remains positive as power costs, which account for one-third of smelting costs, remain high and demand grows. Lehman Brothers said in a recent note Chinese demand could grow by an average of around 13 percent annually until 2020 and keep prices high. "We believe that China will remain an important price driver in the coming years." Zinc was hovering near a two-year low of $1,955 a tonne hit on Friday. It was last at $1,965 from $2,005 on Friday. "Zinc supply is plentiful, and right now the LME inventory is building up," Elliott said. Zinc stocks are up about 60 percent to 144,850 tonnes since the start of January. Tin was trading at $20,350 a tonne from $20,200 on Friday, lead at $1,966 from $1,974/1,975 and nickel was unchanged at $22,100. | 
