OPEC said global oil markets remain well supplied even after its production fell in May for the first time in eight months.

The Organization of Petroleum Exporting Countries, which meets in Vienna this week to discuss its output policy, pumped 31.58 million barrels a day last month, the group’s secretariat said in its Monthly Oil Market Report today. That’s down from 31.64 million barrels in April and exceeds its 30 million quota agreed in December.

“High OPEC crude oil production standing above market requirements provides further confirmation that the market remains amply supplied,” the group said. “Ongoing challenges to world economic recovery have led to even larger uncertainties for oil demand in the second half of this year.”

OPEC, responsible for 40 percent of global oil supplies, will meet on June 14 to decide on production levels for the rest of the year. Concern over Europe’s sovereign debt crisis and slowing growth in emerging markets has caused prices to drop, it said. Brent crude futures declined 15 percent in May and have since slumped 4 percent to trade at $97.52 a barrel today on the ICE Futures Europe exchange in London.

Ali al-Naimi, Saudi Arabia’s oil minister, said yesterday that maybe the group needs to raise its output limit. Venezuela’s Oil Minister Rafael Ramirez said OPEC should keep production quota unchanged.

Output Cut

Saudi Arabia, the group’s biggest exporter, boosted production to 9.92 million barrels a day in May from 9.88 million barrels a day the previous month, according to OPEC estimates which are based on secondary sources. The kingdom said it had cut output to 9.8 million from 10.1 million in April.

The world will consume 88.7 million barrels a day this year, about 900,000 barrels a day, or 1 percent, more than in 2011, OPEC said. That’s unchanged from last month’s report.

Demand for OPEC crude is projected to average 29.9 million barrels a day, a decline of 100,000 barrels a day from 2011 and revised down 30,000 barrels a day from last month.

Supply from outside OPEC will be boosted this year by rising U.S. production to a projected 53.07 million barrels a day, the organization said. That would reflect a 700,000 barrel- a-day increase from last year.

The group’s members are Algeria, Angola, Ecuador, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates and Venezuela.

The International Energy Agency, an adviser to consuming nations, will release its monthly report on global oil supply and demand tomorrow.