He said that Washington wanted the Dec. 3-14 talks, of 190 nations with more than 10,000 delegates, to end on Friday with an accord to start two years of negotiations on a new global climate treaty to succeed the Kyoto Protocol beyond 2012.

A draft final text by Indonesia, South Africa and Australia says evidence by the UN climate panel demands cuts of 25-40 percent by rich nations to avoid the worst impacts of climate change such as more droughts, floods and rising seas.

"We don't want to start out with numbers," Watson told a news conference, adding that the 25-40 percent range was based on "many uncertainties" and a small number of scientific studies by the UN Climate Panel, a Nobel Peace Prize winner.

Other countries such as Japan are also opposed, fearing such stiff goals would choke economic growth.

The Bali talks are trying to agree the principles for a successor to Kyoto, which binds 36 industrial nations to cut emissions, mainly from burning fossil fuels, by five percent below 1990 by 2008-12.

"Our opinion about Kyoto has not changed," Watson said. President George W. Bush opposes Kyoto, saying it would damage the US economy and wrongly excludes 2012 goals for developed nations, such as China, India and Brazil.

Bush says he will join a new global pact.

Yvo de Boer, head of the UN climate secretariat said that the 25-40 percent range would be "critical issue" at the talks. He said he considered the figure an important signpost to show where the world should be heading in curbing warming.

De Boer also said that all industrialised nations agreed on the need to agree a Kyoto successor at UN talks in Copenhagen at the end of 2009. Developing nations, wary of any commitments that might hit their drive to fight poverty, are undecided.

Environmentalists urged action.

"This is the week the world has been waiting for," said Jennifer Morgan of the London-based climate E3G think-tank.

On the margins of the main talks, about 40 deputy finance ministers held unprecedented talks about ways to ensure that efforts to slow climate change do not derail the world economy.

"Having the finance ministers meeting...itself is a breakthrough," Indonesian Finance Minister Sri Mulyani Indrawati said. The meeting will prepare for talks by about 20 finance ministers in Bali on Tuesday.

"The role of the finance ministers is to lead this discussion so that we have wider policy options," Indrawati said, referring to taxes or incentives for green technologies such as wind, solar power or "clean coal".

Trade ministers also met at the weekend, the first time the annual UN climate talks have expanded beyond environment ministers. The trade ministers failed to ease splits between Brazil and the United States over green exports.

The UN Climate Panel, which will collect the Nobel Peace Prize on Monday in Oslo with former US Vice President Al Gore, has said that the strictest measures to offset warming will slow annual world growth by 0.12 percentage point at most.

-- For Reuters latest environment blogs click on: http://blogs.reuters.com/environment/