The chances of reviving stalled global trade negotiations rose Thursday as top officials from five major powers agreed on how to handle the talks concerning the hotly disputed issue of farm trade.

The deal emerged after extended meetings between U.S. Trade Representative Robert B. Zoellick and his counterparts from the European Union, Brazil, India and Australia. It was greeted cautiously by diplomats at the World Trade Organization's headquarters here as the most hopeful sign yet of avoiding a second, potentially fatal, collapse of the Doha Round of negotiations aimed at lowering trade barriers worldwide.

The breakup of a similar meeting in Cancun, Mexico, last September severely set back the negotiations, which began in 2001 and now have little chance of producing a final agreement by the end of this year as had been planned.

Participants in the talks warned that new sticking points have arisen, chiefly involving trade in industrial goods, and there is no guarantee that even the deal on agriculture among the so-called Five Interested Parties will be acceptable to all the WTO's 147 member countries.

Still, the agreement among the five is significant, because those nations represent a diverse and influential group of interests on the central issue of subsidies to farmers in the developed world. India and Brazil have led a group of developing countries in insisting that agricultural subsidies be lowered in the United States, Europe and elsewhere, while U.S., European and other negotiators have been hesitant to cut benefits for domestic producers.

"I welcome the agreement among five key members on the agriculture text," WTO Director-General Supachai Panitchpakdi said in a statement conveyed by a spokesman. "It is an important input into our negotiations and gives momentum to our efforts at completing negotiations. But I must caution that no agricultural framework deal is possible without the consensus of all WTO member governments."

So fluid was the situation tonight that sharply conflicting accounts of what the five had agreed upon circulated, with some sources saying that it included a potentially significant promise by the developed countries for a "down payment" that would cut certain types of farm subsidies by 20 percent. But it was unclear what sort of subsidies that would involve, and what sort of escape hatches would remain for products that the countries want to protect.

The precise wording of the draft was still being debated and the text was being rewritten late into the evening by a small group that included Supachai and Tim Groser, a New Zealand trade diplomat who chairs the agriculture negotiations.

After predicting yesterday that a text would be available this morning, and later predicting that it might come out late Thursday night, Keith Rockwell, the WTO's chief spokesman, said shortly before midnight that the draft was still "hours and hours away" because "a lot of revision, a lot of effort is going into this."

A deadline of midnight Friday had been set for this week's talks, but many participants are angry that the delay in producing a new text means they will have no time to consult with their governments on matters of potentially explosive political concern. Accordingly, officials glumly acknowledged this evening that the deadline could be extended by 24 hours.

Spokesmen for the five powers were silent on the substance of the agreement for fear of fueling resentment among the other WTO members left out of the elite group.

The talks among the five "were very useful and constructive," said Arancha Gonzalez, the spokeswoman for European Trade Commissioner Pascal Lamy. Officials of the five nations emphasized that Groser is consulting with and briefing as many other WTO members as possible before finishing the text, and that, practically speaking, a small group of countries needed to seize the initiative to lead the rest to compromise.

Despite all the haggling, an agreement this week -- should one be struck -- would not change a single tariff, quota or subsidy. The goal of the talks this week is to forge a "framework" that would set the boundaries of future negotiations leading toward those more substantive decisions. Yet at the same time, failure to get even that far would be a setback to the WTO's efforts to promote more open commerce among nations.

Just as optimism surged about the agriculture text, officials said a number of developing countries are balking at a proposed formula for cutting tariffs on industrial goods. The formula would require countries with high tariffs to reduce them much more sharply than countries with low tariffs.

That is a major goal of the United States and the European Union, which hope to swap concessions in agriculture for concessions that would help their big industrial exporters sell their products more easily around the world. But the prospect of freer trade in manufactured products unnerves many developing countries that fear being overwhelmed by competition from China.