PARIS: A new U.S. call for curbing greenhouse gas emissions shook up climate talks Thursday in Paris among the world's biggest polluters, with some envoys welcoming the gesture and others calling it too little, too late.

U.S. President George W. Bush said the United States must stop the growth in its emissions of greenhouse gases by 2025, acknowledging the need to head off serious climate change.

His White House address Wednesday marked the first time he had set a specific target date for U.S. climate pollution reductions. He said he was ready to commit to a binding international agreement on long-term reductions as long as other polluting countries, such as China, do the same.

In Paris, where talks are scheduled through Friday, South African Environment Minister Marthinus van Schalkwyk said Bush's speech "takes us backward," because it did not call for mandatory emissions cuts. Such cuts are central to U.N. negotiations on a follow-up plan to the Kyoto Protocol.

Even tougher criticism came from Germany, whose environment minister said Bush is "lagging hopelessly behind the problems with his proposals."

"His speech follows the motto: 'losership instead of leadership,'" Sigmar Gabriel said in a statement issued in Berlin. "We are glad that there are other voices in the USA."

The meetings in Paris are part of a U.S.-sponsored series of negotiations on global warming. They involve representatives from the countries that produce 80 percent of the world's greenhouse gas emissions, blamed for heating the planet — including the United States, the European Union, China and India.

Bush's chief adviser on climate change, Jim Connaughton, defended the U.S. position at the talks in Paris. "It was a speech directed at domestic audiences," he said. The United States was "way ahead of the curve," on environmental measures such as developing biofuels and environmentally friendly technology, he added.

He acknowledged that Bush's speech had caused tensions at the Paris talks, adding, "we will work through that today."

Bush's aides said the speech was aimed at heading off a "train wreck" of varying legislation in the U.S. Congress.

Delegates from the European Commission and the EU presidency found Bush's strategy "disappointing," said the chief U.N. climate change official, Yvo de Boer.

De Boer said Bush's speech immediately became a central topic at Thursday's closed-door talks. "It is really good that there is a proposal on the table by the United States," De Boer said.

Chinese participant Su Wei said it was good news that Bush was talking about emissions at all. But he added, "to take measures to slow down the increase in emissions is not enough."

The Paris talks were initially meant to focus on reducing trade barriers to environmentally friendly technology, and to working out sector-by-sector targets for cutting global emissions. The South African environment minister said the Bush speech was a "complicating factor" that threw off the agenda.

The Paris sessions are the third in the series of U.S.-sponsored talks after meetings in Honolulu in January and New York in September.