 The United Nations praised on Thursday a step by a US Senate committee to cut greenhouse gas emissions in the world's top carbon emitter even as Washington reaffirmed opposition to mandatory caps. "That's a very encouraging sign from the United States," Yvo de Boer, head of the UN Climate Change Secretariat, said at 190-nation U.N. talks in Bali, Indonesia, of a vote by the Senate Environment and Public Works Committee. His comments underscored the isolation of President George W. Bush's administration at the Dec. 3-14 talks. Australia's new government ratified the Kyoto Protocol on Monday, leaving the United States as the only developed nation outside the pact. Australian Prime Minister Kevin Rudd has also offered to act as a bridge on climate change between China and the West, a Rudd spokeswoman told Reuters on Thursday. China is poised to become the world's top carbon emitter and is not bound by emissions caps under the Kyoto Protocol. Getting China, which is already pursuing energy efficiency targets for its booming economy, to join a broader climate pact is regarded as crucial by many as nations prepare for rising seas, melting glaciers, severe storms and water shortages. The U.S. Senate committee voted 11-8 on Wednesday for legislation outlining a cap-and-trade system for industry, power generators and transport. The bill is headed for debate in the full Senate. "It will not alter our position here," US chief climate negotiator Harlan Watson told reporters in Bali of the vote. Bush says Kyoto would harm the economy and wrongly excludes goals for developing nations until 2012. Instead, he favors big investments in clean technologies but dismisses emissions caps. Watson said Washington was pushing ahead with its own track by inviting big economies to Honolulu, Hawaii, next month for climate change talks after a first Washington meeting in September. He said he believed the dates were Jan. 29 and 30. BALI TO HAWAII Bush wants 17 big emitters, accounting for more than 80 percent of greenhouse gases, to agree to new climate goals by the end of 2008 -- just before he leaves office -- and feed into a new UN pact meant to be agreed by the end of 2009. Delegates in Bali are seeking ways to bind all nations more tightly into a fight against climate change. But China, India and other developing nations say rich countries must commit to deep emissions cuts first. UN Secretary General Ban Ki-moon said he believed in principle there should be mandatory capping. "However, I know there are some concerns in some of the developing countries, therefore this issue should be discussed in the future negotiation process," he told reporters in New York. Ban said the Bali gathering showed there was momentum on the issue, "and, I hope, the political will to act." More than 200 climate scientists from around the world urged nations at the Bali talks to make deeper and swifter cuts to greenhouse emissions, mainly from burning fossil fuels. They said governments had a window of only 10-15 years for global emissions to peak and decline, and that the ultimate goal should be at least a 50 percent reduction in climate-warming emissions by 2050. "We appreciate this is a significant challenge for the world community," Professor Andy Pittman, from the University of New South Wales in Australia, told reporters in Bali. "But it is what is required to reduce the risks of dangerous climate change, and that is what we are all trying to do here." Underscoring the financial risk of global warming, the International Monetary Fund said in Washington it would spell out the economic implications of climate change in research and discussions set for early 2008. "This research will analyze in greater depth the macroeconomic implications of climate change and policy responses to it, both in terms of mitigation and adaptation," Deputy Managing Director Takatoshi Kato said at the Fund's first news conference on the economic effects of warming. Kato will join world leaders in Bali next week. Ban said the Bali process was a chance to engineer eco-friendly transformation of the global economy -- "One that spurs growth and development rather than hinders it, as many national leaders fear."