Possible further trims could come from a meeting of the Group of 20 nations on Friday.

Negotiations hit a snag late Thursday over Mexico’s reluctance to cut its share of oil, reportedly 400,000 barrels a day, leaving the deal in limbo.

Even before that happened, oil prices fell because analysts and traders had hoped for a bigger reduction to prevent the buildup of a glut of oil. On Thursday afternoon, the West Texas Intermediate crude future contract, the American benchmark, was down more than 7 percent to $23.28 a barrel.

Amrita Sen, chief oil analyst at Energy Aspects, a research firm, said markets would not be impressed by the deal.

In addition, the new cuts won’t begin until May, allowing oil supplies to increase. There are also doubts about whether some of the countries party to the cuts, like Iraq, which often produces whatever it can, will really observe them. Ms. Sen said that OPEC and its collaborators were largely doing what they would be forced to do anyway.