Oil edged back above $47 a barrel on Friday after another surge in U.S. crude inventories prompted OPEC to warn of a possible cut in supply next month. U.S. light sweet crude for June delivery gained 43 cents to $47.35 a barrel in Asian trade, erasing Thursday's 33-cent loss. Brent crude oil gained 22 cents to $48.10 a barrel, reversing a 23-cent loss a day ago. Although a sustained build in U.S. commercial crude stocks to their highest level in six years has helped wipe about $11 off prices since early April, dealers said less robust oil product inventories and a refining crunch lent support to the market. "Even if U.S. crude stocks are high, they can't refine everything," said Noboru Kamakura, general manager of risk management at Mitsubishi Corp. The Organization of the Petroleum Exporting Countries warned on Thursday that the cartel might start to rein in supplies above its formal output limits if global oil inventories were building up too quickly. OPEC President Sheikh Ahmad al-Fahd al-Sabah said the group would keep pumping nearly flat out at around 30.3 million barrels per day (bpd) until it meets on June 15 to chart output policy. "If the stockbuild is above the agreed-upon levels, which is the five-year average, then this may be the start of reducing the overproduction," he said. Middle East OPEC producers have been boosting production steadily since March to build a cushion of stocks ahead of a seasonal demand surge in the fourth-quarter winter months. A stronger U.S. dollar and signs of weaker demand growth from China have also pressured oil this month. Speculation of a possible revaluation of China's yuan currency has contributed to fund selling, analysts say.