Mr. Khelil said exporters were having trouble locating buyers for their crude, with some countries finding that normally reliable customers could not obtain letters of credit to finance their purchases because of the financial crisis.

“This slowdown in oil demand is serving to exacerbate the situation in a market which has been oversupplied with crude for some time,” OPEC said in its statement. “Moreover, forecasts indicate that the fall in demand will deepen.”

The drop in prices is affecting exporters and importers in unexpected ways. With fewer petrodollars now flowing to the Gulf, Russia and other regions, a major source of global liquidity and investment in places like the United States and Europe is beginning to shrink.

Even the Saudis, who argued for keeping the markets well supplied at the last OPEC meeting, seemed to have been struck by the speed of the price drop.

When prices spiked this summer, the cartel’s leaders attributed the jump to speculation, and Saudi Arabia, the world’s biggest oil producer and OPEC’s most powerful member, opened the taps and increased production to a record of 10 million barrels a day. The Saudis have since pared their output to around 9.5 million barrels a day, according to analysts.

As the lowest-cost producer, Saudi Arabia can afford to let prices fall for a while without hurting its budget. Most analysts estimate that the Saudis could live with oil at $55 to $65 a barrel. But other producers need higher prices. Nigeria’s oil minister said his country would be more comfortable with $80, Qatar has set a range of $70 to $90, and Iran’s representative said that prices below $90 a barrel would hurt.

For Iran and Venezuela, the drop in prices is particularly painful, because both have been spending freely on the assumption that prices would stay high. A continued drop in oil prices, and a tough domestic economy, could jeopardize the position of Iran’s president, Mahmoud Ahmadinejad, who was elected on a populist platform and who faces re-election next year.