Oil prices held above $51 on Monday and OPEC's president said the cartel will keep pumping near full tilt, ignoring its system of formal production quotas. "I think now we are dealing with the production without the quotas," said Kuwaiti oil minister Sheikh Ahmad al-Fahd al-Sabah, also OPEC President. Robust demand growth in the United States and China has helped propel prices to record highs, despite fears that higher energy costs will ultimately undermine economic growth. Kuwait's Sheikh Ahmad said he believed Saudi Arabia had raised production to almost 10 million bpd this month. OPEC's production surge has helped push U.S. crude stocks to 327 million barrels, their highest level in nearly six years. "Crude stocks will probably keep building until the refineries increase runs to produce more gasoline for the summer driving season by the end of May," said Tony Nunan of Mistubish Corp in Tokyo. OPEC, which controls half the world's crude exports, meets again on June 15 in Vienna to chart production strategy for the second half of the year. Supply growth in other parts of the world has fallen below expectations in part because a surge in Russian output has tailed off.