Negotiators moved closer to a deal to protect the world's forests with a pledge from the United States and five other countries to spend $3.5 billion over the next three years to slow their destruction.

The plan to reduce and eventually reverse deforestation in developing countries is a key component of the global climate pact being negotiated at the U.N. conference in Copenhagen.

The funding announced Wednesday "is what's needed to break the logjam" of negotiations and spark more commitments for the issue, Andrew Deutz of the The Nature Conservancy said in a statement.

The burning or cutting of trees to clear land for plantations or cattle ranches is blamed for about 20 percent of global emissions. That's as much carbon dioxide as all the world's cars, trucks, trains, planes and ships combined.

Progress on the proposal known as REDD, for Reducing Emissions from Deforestation and Degradation, has been hampered by a lack of funding commitments from developed countries. The nations with rainforests want billions more in commitments from wealthy nations.

The United States said it would contribute $1 billion from 2010 to 2012, with Australia, France, Japan, Norway and Britain contributing the rest. U.S. Secretary of Agriculture Tom Vilsack said the money will be available for developing countries that produce ambitious plans to slow and eventually reverse deforestation.

Brazil's lead negotiator on the deforestation deal, Tasso Rezende de Azevedo, said the negotiated text was in good shape after days of confusion and various versions.

"The only question is whether we have a decision on all the topics," he said. "This decision doesn't exist unless you have a decision on the whole thing."

Other delegates said several hurdles remained, including setting benchmarks for deforestation — early targets of 50 percent reductions by 2020 and an end to deforestation by 2030 have been stripped from the text.

Negotiators also must decide whether REDD projects will be done at a national or local level, how to raise the money and, most importantly, the amount of money that will go to the program.

"It is missing funding. It is not in the text and will have to be negotiated at the ministerial level," said Federica Bietta, the deputy director of the Coalition for Rain Forest Nations. The group represents most of the countries that could take part in a forest scheme.

REDD would be financed either by wealthy nations or by a carbon-trading mechanism — a system in which each country would have an emissions ceiling, allowing those who undershoot it to sell their emissions credits to over-polluters.

Brazil wants rich nations to contribute $30 billion in direct aid by 2015, and wants to limit to 10 percent the amount of credits that rich countries can get for investing in forests. Other tropical nations counter that carbon markets should play a bigger role.

About 32 million acres of forests are cut down each year — an area about the size of England or New York State — and the emissions generated are comparable to those of China and the United States, according to the Eliasch Review. Deforestation for logging, cattle grazing and crops has made Indonesia and Brazil the world's third- and fourth-biggest emitters.