The Organization of Petroleum Exporting Countries agreed to raise output quotas 1.8% and promised to supply more soon after four increases in the past year failed to prevent a jump in prices.

The group, which pumps almost 40% of the world’s oil, will raise quotas by 500,000 barrels a day to 28 million a day, Saudi Oil Minister Ali al-Naimi said yesterday in Vienna. Ministers from Iran, Venezuela, and Kuwait said the group is unlikely to produce more, because OPEC already is delivering that amount. The OPEC president, Sheikh Ahmad Fahd al-Sabah, will start talks on the next boost if oil stays above $50 a barrel for seven days.

“The quotas have become meaningless,” said Julian Lee, an analyst at the Centre for Global Energy Studies, a London-based consulting company founded by former Saudi oil minister Sheikh Zaki Yamani. “The only likely way out of $50 to $55 a barrel oil is a dramatic slowdown in oil demand. There’s no new source of supply that’s going to come on stream.”

OPEC members want to lower prices to prevent a further weakening of the world economy, which would hurt oil demand. The International Monetary Fund forecasts world economic growth will slow to 4.3% in 2005 from 5.1% in 2004, and Group of Eight finance ministers last weekend said higher energy costs are a “significant concern.”

Concern that crude oil demand may exceed production later this year has extended to the refining industry as processing plants run close to their limits.

“It’s not just a question of crude supplies, it’s also a question of refining capacity, so there are limits to what OPEC can do to bring down prices,” said William Dudley, chief domestic economist at Goldman, Sachs & Company, in an interview in New York. He reiterated a view from the securities firm that a disruption in supplies may send oil to $105 a barrel.

The Qatari minister said OPEC can do nothing to cut prices.

“The world faces no shortage of supply of oil,” the minister, Abdullah bin Hamad al-Attiyah, said in an interview. “It’s concern about products, like gasoline, diesel. There is a shortage of production of these because of the limitations in refineries. That is the problem that everybody should be paying attention to. How can we solve it? OPEC has no solution.”

No new refineries have been built in about 30 years in America and about a decade in Europe. Environmental concern and local opposition to new plants is preventing construction. Saudi Arabia’s Mr. al-Naimi called for more investment in the refining industry to handle lower-quality oil.

“The last thing I’d be in this market would be short,” said Boone Pickens, the Dallas hedge fund manager and former oil executive. Any additional OPEC supply will be “undesirable oil that refineries won’t want. It’s unlikely that kind of oil will even go into the market.”

Because of high prices, Exxon Mobil, BP, Royal Dutch/Shell, Chevron, and Total reported last year net income of about $85 billion.