At U.N. climate talks in Barcelona, Spain, African nations walked out of meetings to protest rich nations' reluctance to make substantial carbon-cutting commitments. In Washington, some conservative Republicans boycotted the start of committee debate on a bill to curb greenhouse gases, fearful of the cost to the U.S. economy.

German Chancellor Angela Merkel, in a bid to support the Democratic-sponsored climate bill, told a rare joint session of Congress that "there is no time to lose" in tackling climate change.

But the lukewarm response to her comments on global warming - in contrast to the ovations she received at other times - underscored the skeptical mood in the United States about climate action, which would require a shift away from fossil fuels to wind and solar power, smaller cars, and - the Republicans argue - more expense to consumers.

GOP senators on the Environment and Public Works Committee shunned the planned start-up of voting on amendments to the bill. Only Sen. George V. Voinovich, (R., Ohio) showed up, for 15 minutes, to explain that Republicans demand a closer analysis of the bill's cost and impact on jobs.

African countries ended their boycott of meetings in Spain at U.N. climate talks, only after resetting the agenda to spend more time on complaints that industrial countries had set carbon-cutting targets too low for reducing global greenhouse-gas emissions.

The actions raise doubts on how much the 192-nation conference in Copenhagen, Denmark, will achieve during its Dec. 7-18 meeting, which is meant to adopt a treaty regulating carbon emissions that will shake economies around the globe.

The African revolt was largely symbolic, since it was clear industrial countries cannot alter their positions without high-level decisions by governments. But it was a signal that hard-liners would dominate talks by the developing countries at the Copenhagen forum.

The White House and Democratic leaders in Congress have essentially abandoned prospects of getting a climate bill to President Obama's desk before the Copenhagen meeting. But they hope a show of eventual progress in the Senate, along with the House having passed a bill and Obama's call for more fuel-efficient cars, will show the world the United States is taking climate change seriously.

Scientists say industrial countries should reduce emissions by 25 percent to 40 percent from 1990 levels by 2020, but the targets announced so far amount to far less than the minimum. The Africans say that new climate studies show the dangers are even greater than thought just a few years ago and that industrial nations should reduce emissions by at least 40 percent by 2020.

The U.S. delegation refuses to say what its figure will be until it gets a green light from Congress.

The Democratic bill that was to have gotten a hearing yesterday calls for cutting emissions from power plants and industrial facilities 20 percent by 2020 and 83 percent by midcentury. Polluters would be given pollution permits that they could trade among themselves to ease the economic effect of the transition from fossil fuels.

President Obama, after a day of meetings with the German leader and other European Union leaders, reiterated his determination to join an international climate regime. "The United States, Germany, and countries around the world, I think, are all beginning to recognize why it is so important that we work in common in order to stem the potential catastrophe that can result if we continue to see global warming continue unabated," he said.

The Copenhagen measure would succeed the 1997 Kyoto Protocol, which called on 37 industrial countries to reduce heat-raising gas emissions by an average 5 percent below 1990 levels by 2012. It made no demands on developing countries such as India and China. The United States is the only country that has not signed on to the pact.