(Updates with official prices) LONDON, April 28 (Reuters) - Copper eased from 10-year highs on Wednesday ahead of a policy announcement by the U.S. Federal Reserve, but analysts at Goldman Sachs joined others predicting a rally to record levels. Benchmark copper on the London Metal Exchange (LME) was down 0.3% at $9,823.50 a tonne in official trading after reaching $9,965 on Tuesday, the highest since 2011. Prices have more than doubled since March 2020 as the world economy rebounds and the shift to greener, more copper intensive energy raises the prospect of supply shortages. “It is only a question of time before it exceeds the psychologically important $10,000 mark,” said Commerzbank analyst Daniel Briesemann, adding that the all-time high of $10,190 would be likely be breached shortly afterwards. But he said the rally looked overstretched a sharp correction was likely before copper rises further in the years ahead. GOLDMAN: Goldman Sachs forecast copper would average $9,675 a tonne in 2021, $11,875 a tonnes in 2022 and $12,000 a tonne in 2023. CHILE: The threat of strikes at copper mines in Chile receded after the country allowed another drawdown in pensions, pleasing workers. SUPPLY OUTLOOK: Ample supplies next year and in 2023 will keep the market balanced, but miners need to start investing in new capacity now to meet a pick up in demand growth. MARKETS/FED: World shares were near record highs and the dollar and global bond yields nudged higher. Markets will be watching for signs that the Fed will tighten policy in a statement due at 1800 GMT. TIN: LME tin was up 2.1% at $27,706 a tonne after reaching $27,850, its highest since 2011. Supplies are short, with stockpiles in LME-registered warehouses at just 1,300 tonnes. MSNSTX-TOTAL OTHER METALS: Aluminium was up 0.1% at $2,397.50 a tonne, zinc was flat at $2,926, nickel added 1.8% to $17,262 and lead was 0.4% higher at $2,097.50.