Boycotts on either side of the Atlantic on Tuesday showed just how difficult it will be to clinch an agreement on global warming next month.

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 “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 — only 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.

Republican senators on the Environment and Public Works Committee shunned the planned startup of voting on amendments to the bill. Only Sen. George Voinovich showed up and he stayed only for 15 minutes to give the reasons for the Republicans’ absence.

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

The parallel actions were elements of a dramatic finale leading up to the 192-nation conference in Copenhagen on Dec. 7-18, 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 that industrial countries cannot alter their positions without high-level political decisions by governments.

But it was a signal that hard-liners would dominate negotiations by the developing countries at the decisive Copenhagen forum, and marked the 50-nation African group as an influential player on the global stage.

The Africans, supported by about 70 other developing countries, including China, say the industrial world is failing to live up to pledges of deep cuts in emissions, while droughts and floods already are causing death and devastation on the badly hit continent.

“I don’t think we can get to a result in the way we’re going now,” said Algerian negotiator Kamel Djemouai, who chairs the Africa group. “The figures that are now on the table are not really ambitious.”

The White House and Democratic leaders in Congress have essentially abandoned prospects of getting a climate bill to President Barack Obama’s desk before the Copenhagen meeting. But they hope a show of 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 U.S. is taking climate change seriously.

U.N. Secretary-General Ban Ki-moon acknowledged the climate change treaty may not be resolved this year, adding that nations may be unable to commit to firm emissions limits at Copenhagen.

“We may not be able to agree (on) all the words,” Ban said after meeting in London with British Prime Minister Gordon Brown. Ban said he would push leaders to strike a pact in Copenhagen, but that it was more likely to be an agreement on principles — rather than specific targets for cuts.

“We need at this time the political will — if there is a political will, there is a way we can come to a binding agreement in Copenhagen,” Ban said.

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 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 has refused to say what its figure will be until it gets a green light from Congress.

“It’s really good that the Africans have finally been able to stand up together,” said Fiona Musana of Greenpeace Africa. “That sends a strong signal.”