By ELISABETH ROSENTHAL

Just as the world seemed poised to combat global warming more aggressively, the economic slump and plunging prices of coal and oil are upending plans to wean businesses and consumers from fossil fuel.

From Italy to China, the threat to jobs, profits and tax revenues posed by the financial crisis has cast doubt on commitments to cap emissions or phase out polluting factories.

President-elect Barack Obama and the European Union have vowed to stick to commitments to cap emissions of carbon dioxide and invest in new green technologies, arguing that government action could stimulate the economy and create new jobs in producing sustainable energy.

But the political will and the economic underpinnings for a much more assertive strategy appear shakier than they did even a few weeks ago.

“Yes things have changed,” said Yvo de Boer, executive secretary of the United Nations Framework Convention on Climate Change, in a telephone interview.“European industry is saying we can’t deal with financial crisis and reduce emissions at the same time,”he said.“Heads of government have other things on their minds.”

The economic decline also could complicate the political calculus of limiting emissions in developing countries, especially China.

China overtook the United States as the largest producer of greenhouse gases in 2007. But the surge in heavy industry there that produced a sharp increase in its emissions already has given signs of a slowdown.

Some experts argue that China’s emissions - and the pressing need to limit them - may recede until economic conditions improve.

Mr.de Boer said he remained optimistic that major powers would keep their pledges to reduce emissions.

“I don’t think anyone will show the stupidity to focus on the short term and ignore the long-term issue because these decisions will be with us for 30 years,”he said.

Even so, there are signs of considerable rethinking of at least near-term commitments to invest in green technology and alternative energy.

Italy’s environment minister, Stefania Prestigiacomo, said last month that“profound changes”were needed in the European Union climate package because of the global economic crisis. Coal-based economies like Poland’s have similar worries.

Barbara Helfferich, the European Commission spokeswoman on the environment, said,“Investing in reducing emission is more difficult to do in times of economic downturn than when you have money to spend.”

The European Commission says it is planning to stay its course toward lower emissions - a 20-percent reduction by 2020 - and in so doing hopes to have a“first mover advantage” in terms of job creation, renewable sources and energy innovation once the global economy rebounds.

“I know it sounds counterintuitive, but our argument is that because there is an economic turndown, it is just the time to tackle the transition from a high-carbon to a low-carbon economy,”Ms.Helfferich said.

Yet the current economic slump could have serious long-term environmental consequences, because it may reduce investment in greener production technologies without fundamentally changing the longer-term emissions picture. With so many renewable energy projects and programs in their nascent stages, their success is easily undercut by lack of credit or financing.

Wind costs more than $2.5 billion per gigawatt to build, compared with $600 million for gas. Carbon permits and subsidies can narrow that gap, but the current low prices mean that it is cheaper to burn coal, even after paying penalties for the carbon dioxide emissions.

The United Nations says that 40 percent of the world’s power generating capacity has to be replaced in the next 5 to 10 years. Six months ago, high oil prices, easy credit and political pressure led many governments to promote biofuels, wind farms and nuclear projects and phase out fossil fuel plants. But the logic of spending more on such plants has at least partly evaporated.

“If because of the current economic scenario, you choose cheap and dirty, we’ll be in big trouble,”Mr.de Boer said.

The European Union estimates that it will cost Italian industry 13 billion euros, about $16.7 billion, to reduce emissions. Italy puts the cost up to 27 billion euros, which is says it cannot afford.

“Transitions are expensive, but this one will help avoid the ups and downs we’ve recently seen,”Ms.Helfferich said.“This is a short-term bitter apple to create new sectors that are conducive to fighting climate change and jobs as well.”