BANGKOK, Thailand — When it comes to climate change, the United States has commitment issues.

At least that’s the position taken by most developing countries, which accuse the U.S. of stalling a global effort to ward off catastrophic global warming.

A nearly 200-nation United Nations effort to cool the planet has already agreed on a core goal: preventing earth from heating up by more than 2 degrees Celsius (3.7 Fahrenheit) above pre-industrial temperatures.

But a summit this week in Thailand’s capital ends with dimmed hopes that the world’s governments will ever agree on a legally binding plan to pull that off.

Developing world delegates in Bangkok repeated their familiar refrain: Though the U.S. has produced the most planet-warming pollutants, poorer nations will bear the extreme weather, flooded coasts and crop losses brought on by global warming.

“It’s insane,” said Bolivia’s U.N. Ambassador Pablo Solon. “We have such a challenge facing climate change and we’re losing time.”

But America won’t chain itself to a legally binding agreement to limit emissions unless other major polluters — namely China, Russia and India — agree to the same limit, said U.S. climate negotiator Jonathan Pershing.

The U.S., which pumps out nearly 20 percent of the world’s planet-warming gases, is no longer the biggest polluter. It’s China, which emits 22 percent of all green house gases, according to the U.N.

“We are not prepared to go forward with a binding obligation for ourselves that would not apply to other major economies,” said Pershing, who characterized both China and India as similarly reluctant to commit.

U.N. delegates gathered in Bangkok to hash out a sweeping climate change plan before the year’s end when they regroup in South Africa.

But they are leaving with a proposal little changed from their last meeting in Mexico. At that December summit, delegates signed off on a goal to limit warming to no more than 2 degrees Celsius over pre-industrial levels.

That, they agreed, will prevent some of the worst effects of climate change: dried-up crops, fast-rising seas and extreme weather events. They also approved a $100 billion fund to help poorer nations cope with climate change.

Environmentalists and many developing nations, however, were hoping for more out of this week’s gathering.

Even the 2-degree goal will seriously alter the environment for the worse, said Lim Li Lin, an environmental researcher with the Third World Network.

The U.S. has chosen to “domestically determine what they’re politically prepared to do, not what science has determined,” Lin said. “It will have catastrophic impacts on our planet and humanity.”

America’s refusal to enact badly needed emissions cuts, Lin said, is too often blamed on a U.S. population unwilling to stomach lifestyle change. “It’s an excuse for inaction,” she said. “They’re basically blaming their domestic constituencies.”

The summit also leaves an uncertain future for the Kyoto Protocol, the world’s first and only legally binding framework on climate change. It expires next year.

Adopted in 1997, and enacted in 2005, it requires 191 nations to collectively cut emissions by 5 percent compared to 1990 levels. But it is also flawed. The U.S. did not sign it. And major polluter China is exempted along with many other developing nations.

Though environmentalists are desperate for a Kyoto 2.0, the Bangkok summit saw confirmations from world powers Japan, Canada and Russia that they would not sign on for a second round.

The protocol will now almost certainly expire without a successor in place, said U.N. climate chief Christiana Figueres, who warned that nations’ individual climate change promises could not solve the problem.

“No country can hope to go it alone,” she said.

In lieu of such a hard and binding treaty, as is favored by much of the developing world, the U.S. will pursue a looser agreement, Pershing said.

With the 2-degrees Celsius target in place, the world’s nations can devise individual plans to reach that goal and regroup under the U.N. to monitor their progress.

“All parties have to be pragmatic. We can’t always allow ideology to stand in the way,” Pershing said. “It’s not a function of whether you did or didn’t emit in 1900.”