The Saudis and their allies argue that to cut production now to raise prices would be to subsidize competitors like the companies extracting oil from shale in the United States, which are responsible for recent big additions to world oil supplies. The Saudis, whose costs for producing oil are low, are betting that low prices will lead to a shakeout of higher-cost producers like the shale companies. At the least, the Saudis appear to want all of OPEC to participate in any trims, analysts say.

Various forecasters have been stoking market fears by issuing forecasts of a growing glut next year. OPEC sent a shudder through the markets Wednesday when it forecast that demand for its own crude would be well below the ceiling that it recently declined to lower.

On Friday, the International Energy Agency, in Paris, said in its December oil market report that demand was likely to be 230,000 barrels per day less than previously forecast. The main reasons for the lowered forecast were less oil consumption in countries that produce it like Russia and a weaker-than-expected global economy.

A trim of 230,000 barrels per day is minimal in a global market of about 93 million barrels per day. But the lower forecast, the fourth by the agency in the past five months, reinforced the sentiment that supply is likely to exceed demand substantially next year.

The drop in oil prices is a blessing and curse for Europe, which is struggling to break free of the economic stagnation that has dogged the region since the global financial crisis.

The European Central Bank is fighting to keep inflation in positive territory, and falling fuel prices, while providing a stimulus to consumer spending, also contribute to the deflationary pressure in the region. Inflation is near zero in the eurozone, and Mario Draghi, the E.C.B. president, is under increasing pressure to enact radical monetary stimulus measures to keep prices from contracting.

Olivier Jakob, an oil analyst at Petromatrix, in Zug, Switzerland, said that he had expected Brent prices to fall no lower than $60 a barrel, but that now it appeared that floor might be breached. Even if market momentum carries it below that $60 level for a time, he said, “it would be difficult to sustain,” because producers would take action, perhaps by cutting output, and some marginally profitable operations would be forced to shut down.