SINGAPORE, March 27 (Reuters) - Sentiment in the Middle East crude market weakened on Tuesday on the prospect of lower demand, after one of three crude distillation units (CDUs) at Royal Dutch Shell's Singapore refinery remained down following a power failure a day earlier. The outage on Monday occurred after electricity supply to the 500,000 barrels-per-day (bpd) plant, Shell's largest in the world, tripped momentarily, called a power dip, resulting in a fire in one of the smaller secondary cracking units. Oman crude futures extended its losses to settle below a premium of $2.00 a barrel to Dubai quotes by 0830 GMT, down 20 cents, Reuters data showed. But the impact of the outage was partly offset after Japan's Cosmo Oil said on Tuesday it has restarted the 120,000 barrels per day No.2 crude distillation unit (CDU) at its quake-hit Chiba refinery for a preliminary test and expects to start commercial production of oil products soon. Cosmo was believed to have bought Iraqi Basra Light crude for May-loading in anticipation of the refinery's restart, a trader said, although this could not be confirmed. Poor refining margins and arbitrage inflows of Russian crude have also weighed on the market, and with trading of May cargoes wrapped up, market participants are looking towards the next round of official selling prices from Middle East producers next week. * TRADES - Shell bought 13 Dubai partials for May at $123.15-$123.60 a barrel. Vitol bought three Dubai partials at $123.15-$123.60 a barrel. Vitol bought 2 partials at $123.10-$123.25, while Trafigura bought 4 partials at $123.16-$123.20. * MARKET NEWS - South Sudan said the Sudanese air force had bombed the main oil fields in Unity state near the border with Sudan on Tuesday, as violence between the two escalated. - A growing gas cloud from a leak at a platform operated by Total off Scotland has forced Shell to remove some workers from two nearby rigs for safety reasons. - Deutsche Bank on Tuesday raised by $2 its 2012 Brent crude oil forecast, partly due to supply disruptions, but lowered its U.S. natural gas price forecasts due to plentiful supply. CRUDE Price Prev Change % change MAY Oman diff to Dubai 1.74 2.15 -0.41 MAY Brent 125.64 124.9 0.69 0.55% MAY Dubai 121.59 120.8 0.78 0.65% MAY DME Oman 123.33 122.9 0.37 0.30% MAY Brent/Dubai EFS 4.05 4.14 -0.09 PRODUCT CRACKS Price Prev Change APRIL gasoil crack -6.92 -7.10 0.18 APRIL fuel oil crack 14.96 14.91 0.05 MAY naphtha crack -8.14 -7.27 -0.87 COMPLEX REFINERY MARGINS Today 5.77 Last 5 days 5.27 Lat 365 days 7.75 (Reporting by Francis Kan; Editing by Sugita Katyal)

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