LONDON, April 26 (Reuters) – Zinc prices were pushed lower on Thursday by rising inventories while aluminium extended losses as investors priced in a loosening of U.S. sanctions affecting giant Russian producer Rusal. Zinc stocks in warehouses certified by the London Metal Exchange have jumped 26 percent this week after rising by a further 18,675 tonnes on Thursday. The amount of cancelled inventory — stock earmarked for delivery — was very low at 5.4 percent, LME data showed. “The real interesting data point is not just the arrivals but (the) cancelled stock,” said Oliver Nugent, commodities strategist at ING in Amsterdam. “You had deeply held trader stocks and those stocks have now been unwound, so that makes metal more available and the tightness is coming off the boil.” In February Zinc touched its highest in more than a decade at $3,595.50 a tonne on supply concerns after closures and suspensions of big mines in recent years, but many operations have resumed production. Benchmark LME zinc fell 1 percent to $3,104 a tonne in official open-outcry trading, having dropped by 2.4 percent on Wednesday. * CHINA ZINC: Shanghai zinc was the biggest loser in the base metals complex, closing 3 percent down at 23,685 yuan a tonne. * LME ALUMINIUM: Three-month LME aluminium, untraded in official rings, was bid down 1.8 percent at $2,205.50 as investors continued to liquidate after the extension this week of the deadline for compliance with U.S. sanctions on Rusal , one of the world’s biggest aluminium producers. The metal is down about 18 percent from the $2,718 seven-year high hit on April 19 after the original sanctions announcement raised concern over potential aluminium shortages. * LONG POSITION: The speculative long position in LME aluminium was estimated to have retreated to 21 percent of open interest by Tuesday’s close, down from 26 percent a day earlier, Alastair Munro at broker Marex Spectron said in a note. * ALUMINIUM PREMIUM: The U.S aluminium premium on Comex was at 21.4 cents per pound ($472 a tonne) on Wednesday, down from the three-year high of 22.1 cents hit on April 11. * DOLLAR: Most other base metals also traded lower, with strength in the dollar making metals more expensive for holders of other currencies. * PRICES: LME copper was bid down 1.1 percent at $6,928 a tonne in official activity, lead traded up 0.1 percent at $2,308, nickel dropped 1 percent to $14,000 and tin firmed by 0.2 percent to $21,300.