The International Energy Agency said on Wednesday it was cutting its oil demand estimates again as the global economic outlook darkens, with significant downside risks. The IEA reduced its global economic growth estimates for 2011 to 3.8 percent from the 3.9 percent given in its September monthly report, with 2012 down to 3.9 percent from 4.2 percent. The IEA, which advises the developed countries on energy policy and developments, said even these growth forecasts, which have slipped steadily, came with \"significant downside risks.\" As a result, it cut its oil demand estimate for 2011 by 50,000 barrels per day to 89.2 million bpd, giving a gain of 1.0 mbpd over 2010, while 2012 was lowered by 210,000 bpd to 90.5 mbpd, up 1.3 mbpd. On Tuesday, the OPEC oil cartel cut its world demand forecasts for 2011 and 2012 for the third time in a row, citing uncertainty in the global economy and weaker demand from developing giants China and India. The Organisation of Petroleum Exporting Countries revised its 2011 estimate down to 87.81 bpd, although it remained 0.88 million mbpd up from last year. In September, the cartel set world oil demand for this year at 87.99 mbpd. For 2012, it put demand at 89.01 mbpd, down from its September forecast of 89.26 mbpd. \"The economic downturn is taking its toll on world oil demand, especially in the OECD (group of developed countries),\" OPEC said in its monthly report. On the supply side, the IEA said world oil output fell by 0.3 mbpd in September from a month earlier to 88.7 mbpd, 1.0 mbpd less than a year ago. The agency said OPEC oil supply fell slightly by 20,000 barels a day to 30.15 mbpd in September, with lower ouptput in Saudi Arabia and Nigeria only partially offset by ramped up production in Libya. \"Libya\'s return to the global market may have already set in motion a rebalancing of production flows for several OPEC member countries which stepped in to fill the breach after hostilities broke out last February,\" the IEA said in the report. \"Saudi Arabia, which increased output by around 1.0 mbpd in recent months, appears now to be scaling back supplies,\" it said. Production in Libya, which produced 1.6 mbpd before the hostilities, was resuming faster than expected even though fighting remained in certain holdouts of fighters loyal to former leader Moamer Kadhafi, the IEA said. Despite \"still formidable challenges\" and continued fighting, the IEA said output had returned to around 350,000 bpd a day since production relaunched in early September. \"Production (in Libya) now looks on track to reach an average of 400,000 bpd in the fourth quarter of 2011, with year-end output closer to 600,000 bpd,\" the IEA said. The agency had earlier forecast output of 350,000 to 400,000 bpd at the end of the year.