In a last-minute turn in global climate talks, international negotiators agreed over the weekend to adopt more ambitious plans than expected to trim government subsidies to oil companies worldwide, part of a broader effort to reduce greenhouse-gas emissions.

Earlier this week, negotiators were hammering out an agreement among the top 20 industrialized and emerging nations that called for each to take “voluntary” measures to cut production and consumption incentives.

But privately under pressure from the Obama administration over the last two days, the group now is preparing to sign an agreement that omits the word “voluntary.”

In another change in the language of the proposed agreement, the pact will pledge an ongoing review process that evaluates how well countries are living up to their commitment.

The tougher language was seen in part as a reaction to the ongoing oil spill crisis in the Gulf of Mexico.

The statement containing the new agreement was described by officials close to the negotiations Sunday afternoon as the final communique was being pieced together. The agreement’s climate passage will be part of a more sweeping statement that will be issued by members of the G-20 nations shortly before they wrap up their summer summit Sunday evening.

Much of the weekend gathering has focused on reaching a group consensus on how to counter the global economic crisis. On that point, leaders appear headed toward a joint statement Sunday afternoon that embraces a commitment to economic stimulus as well as to fiscal austerity.

The communique will likely set a goal of cutting deficits in government spending in half by 2013, officials say, and putting debt on a downward slope by 2016.

In a letter to other leaders last week, Obama said the U.S. would pursue economic recovery while also reducing the U.S. deficit to 3% of gross domestic product by the 2015 fiscal year.

Officials who have seen the communique say it reflects President Obama’s suggestions.

In any version, a summit communique has little real force of its own and is effective only according to how strictly nations decide to abide by its tenets. And Sunday’s statement will not lay out in great detail how and when countries will cut subsidies.

As now crafted, the communique will say that the leaders “encourage continued and full implementation of country-specific strategies and will continue to review progress toward this commitment at upcoming summits.”

Although not binding, the wording is significant to the parties, both as a reflection of the commitment of the world leaders and for its power to shape future conversations.

Where the climate passages are concerned, activists have been concerned for several days now about the explicit use of the word “voluntary” to describe the countries’ commitment to cutting subsidies.

It came across to many as a step back from the agreement of a G-20 meeting last year in Pittsburgh, where leaders formally proposed phasing out subsidies for fossil fuels. Environmentalists were especially upset about it in light of the gulf oil spill.

“That was a signal of weakening,” said Jake Schmidt, international climate policy director of the National Resources Defense Council. “It doesn’t have the same political ‘oomph,’ and lacks the political signal that the countries are expected to live up to it.”

cparsons@latimes.com