The Organization of the Petroleum Exporting Countries forecast that demand for OPEC oil will average 29.21 million barrels per day (bpd) in 2015, up 430,000 bpd from its previous forecast. The group also slashed its outlook for crude supply growth in non-OPEC countries.Oil prices have been trying to find a floor after a brutal selloff that wiped out over half of the market's value since June. The rebound came after weeks of decline in the U.S. oil rig count, which hit three-year lows last week.While most traders cited short-covering as prices continued to advance on Monday from near six-year lows, some noted options expiry in Brent's front-month contract and a weaker dollar as other supportive factors.Brent's premium to U.S. crude narrowed for the first time in five sessions as U.S. futures outperformed on expectations that the oversupply might be resolved sooner than thought due to the falling rig count.Some traders remain pessimistic about the rally. "It was mainly hedge fund, speculator driven and smacks of price-overshooting," said Anuraag Shah, portfolio manager at the Los Angeles-based Tusker Investment Fund, which manages nearly $100 million across commodities. Citigroup said in a note that U.S. crude could fall well below $40, "perhaps as low as the $20 range for a while". On the other hand, the United States will remain the world's top source of oil supply growth up to 2020, even after the recent collapse in prices, the International Energy Agency said, defying expectations of a more dramatic slowdown in shale growth.The agency also said in its Medium Term Oil Market report that oil prices, which slid from $115 a barrel in June to a near six-year low close to $45 in January, would likely stabilize at levels substantially below the highs of the last three years. Standard & Poor's slashed its forecast for average Brent oil price to $55 per barrel for 2015, from its earlier forecast of $105. Crude oil prices have plunged since June, reacting to rising global output at a time of slowing demand, although they have recovered partially in the last few weeks.Standard & Poor's lowered its sovereign credit ratings on Bahrain as well as Kazakhstan and Oman, while lowering its outlook on Saudi Arabia. Standard & Poors' negative outlook for Saudi Arabia due to the decline in oil prices also led to speculation that the No. 1 crude exporter might want the market to recover after its freefall in recent months.Oil producers' organization OPEC, which counts Saudi Arabia as one of its prominent members, decided late last year to maintain its output despite slowing demand.OPEC sharply raised a forecast of demand for its oil in 2015, saying the drop in prices would affect production in the United States and other countries faster than earlier thought.Supply from OPEC has averaged 30.37 million barrels per day (bpd) in January, up from a revised 30.24 million bpd in December, according to the survey based on shipping data and information from sources at oil companies, OPEC and consultants.The ratings agency also said it did not expect Malaysia to be hurt by oil prices, affirming the country's outlook, citing the fact that the Malaysian economy would be able to protect itself against a weakened energy market.