Brazil announced at the summit a "voluntary commitment" to reduce CO2 emissions by between 36.1 and 38.9 percent in the next ten years.

The new law, however, is subject to several decrees setting out responsibilities and regulations for the farming, industrial, energy and environmental sectors.

Lula is expected to sign the decrees in January after consulting scientists and other experts, officials said.

Despite its ambitious targets, Greenpeace's top representative in Brazil, Sergio Leitao, called it merely a list of good intentions and accused Lula of using double standards in environmental issues.

"Brazil usually makes good speeches on the international stage, as in Copenhagen, but in practice it doesn't keep its word," he told reporters.

Before signing the new law, in fact, Lula vetoed three of its provisions, including a reference to "promoting the development of clean energy sources and the gradual phasing out of energy from fossil fuels."

Environment Minister Carlos Minc said he was was pleased with the new law because it showed Brazil's determination to respect the pledges it made in Copenhagen.

"It doesn't matter if the Copenhagen summit didn't get the results we wanted. We will still meet our goals," he told reporters.

The climate change conference held in the Danish capital ended last week with a non-binding agreement that exposed the stark divide between rich and developing nations.

A total of 30 billion dollars was pledged from 2010-2012 to help poor countries in the firing line of climate change, and rich nations set a goal of providing 100 billion dollars annually in aid by 2020.

It established a goal of limiting warming to two degrees Celsius (3.6 degrees Fahrenheit), but did not impose binding targets to reduce the emissions of gases that scientists say are heating up the world's atmosphere to dangerous levels.

The Copenhagen agreement was put together by leaders of the United States, China, India, Brazil, South Africa and major European nations, after it became clear the 194-nation summit was in danger of failure.

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