Oil prices inched up from a three-month low on Tuesday, but expectations that swollen crude stockpiles in the United States would build again kept up the pressure. U.S. crude rose 12 cents to $48.73 a barrel. Prices have closed between $48.54 and $48.67 in each of the last three sessions, but are down more than 6 percent from a week ago. The market touched $47.60 on Monday, its lowest level since Feb. 18. U.S. crude oil stocks, already at their highest level since July 1999, were expected to rise another 1.0 million barrels in the week to May 13, a preliminary Reuters survey of nine analysts forecast. Government data are due out on Wednesday. "The market looks weak fundamentally, as we expect to see another crude inventory build in the United States," said Tony Nunan, a manager at Mitsubishi Corp.'s international petroleum business. "It will put more weight on the market." Oil has slumped nearly $10 from it's all-time high of $58.28 a barrel as the Organization of the Petroleum Exporting Countries boosts supplies to nearly their highest levels in 25 years. On Sunday, OPEC President Sheikh Ahmad al-Fahd Al-Sabah said the cartel was keeping oil markets well supplied and had enough production reserve to meet higher fourth-quarter demand. Saudi Arabia has led the charge, but state oil firm Saudi Aramco's crude oil production is still not in excess of 10 million barrels per day (bpd), President and Chief Executive Abdallah Jumah said on Monday. Aramco boosted its May supplies, putting Saudi production near a daily total of 10 million barrels, industry sources say. Despite the robust production and stockpiles, oil traders are anxious about a variety of factors later this year. A U.S. weather forecast on Monday predicted that up to 15 tropical storms and hurricanes would form in the Atlantic and Caribbean this year, possibly heralding another difficult season for the oil- and gas-producing Gulf of Mexico after last year's storms knocked out oil platforms for months.