World leaders gathered here for a global summit meeting on climate change made modest proposals on Tuesday for combating the problem, underscoring the way domestic political battles still trump what United Nations officials had hoped would be a sense of global urgency.

The negotiations for a new international agreement to curb emissions of greenhouse gases have stalled, making an agreement in Copenhagen by December difficult. In calling the conference, Ban Ki-moon, the United Nations secretary general, asked heads of state and government both in public and in private to set aside national concerns and become “global leaders.”

In speech after speech, presidents and prime ministers of countries large and small spoke with soaring promises about the importance of confronting the problem for future generations. But when it came down to the nuts-and-bolts promises of what they were prepared to do in the next decade, experts and analysts were disappointed that there were no bold new proposals, particularly from the United States.

“It was really great to have the vision, but with just 70 days left to Copenhagen, it is time to put some substance on the table,” said Steve Howard, the founder of the Climate Group, an international organization pushing for a climate change agreement. “The two most important countries on this issue are being guarded in their positions.”

Those two countries — the United States and China — account for more than 40 percent of the carbon emissions, roughly divided between both.

Speaking at the green marble lectern of the General Assembly chamber, President Obama told the audience of some 100 heads of state and government that “unease is no excuse for inaction.”

China’s president, Hu Jintao, spoke of reducing the “carbon intensity” of his fast-growing economy, or cutting emissions as a percentage of future economic output, by a “notable” margin that he did not specify.

Mr. Obama acknowledged that the United States once played down the issue, but now recognized its gravity. The world “cannot allow the old divisions that have characterized the climate debate for so many years to block our progress,” he said, adding that forging consensus would come slowly. “And so all of us will face doubts and difficulties in our own capitals as we try to reach a lasting solution to the climate challenge.”

In a shift of emphasis, Mr. Obama divided developing nations into two categories. The nations with a strong industrial base — countries like China, India and Brazil, although he did not name them — would need to accept curbing their emissions in any agreement. But the poorest nations, he said, deserve financial and other aid to tackle current climate problems and future green development.

Mr. Obama said he was committed to having the United States make its largest investment ever in renewable energy, to setting new standards for reducing pollution from vehicles and to making clean energy profitable, among other initiatives.

The United States is considered essential to success in Copenhagen. It never joined the 1997 Kyoto accord, the first major attempt to limit emissions in a global treaty, partly because the accord did not set mandatory targets for powerhouse developing states like China.

In his speech, President Hu of China said his nation would take four steps toward greener development. He said China would reduce the amount of carbon dioxide it emits to produce each dollar of gross domestic product by a “notable margin” by 2020 compared with 2005 levels; increase forests by 40 million hectares (about 98.8 million acres); increase nuclear or nonfossil fuels to 15 percent of power by 2020 and work to develop a green economy.

Analysts gave China credit for taking carbon emissions more seriously. Its leaders now accept the need to reduce pollution, partly because their country is vulnerable environmentally and partly because they hope to become leaders in green technology. But Mr. Hu neither defined “notable” nor accepted any binding cuts on emissions. He also tied the emissions reduction effort to the growth in China’s gross domestic product, so the amount of emissions per dollar of output — or “carbon intensity” — might shrink, but the overall number could still rise as the economy expanded.

“Developing countries need to strike a balance between economic growth, social development and environmental protection,” President Hu said.

Todd Stern, the United States envoy for climate change, reflected the general reaction to the Chinese proposal by saying, “That can be good, but it all depends on what the number is.”

The president of India did not attend, but the country’s environment minister, Jairam Ramesh, told reporters that the government hoped to enact a series of measures that would curb emissions, including new building codes, limits on deforestation, reductions in greenhouse gases generated by agriculture and increases in renewable sources of energy to 20 percent by 2020 from 8 percent now.

Mr. Ramesh said the lack of specific promises from Mr. Obama should not have been a surprise because like India, the United States is a democracy in which actions depend on popular approval.

The prospect of action by the United States Senate this year appears dim, with Congress mired in the fight over health care and Democrats divided on climate change measures. In late June, the House passed a climate change and energy bill sponsored by two Democratic representatives, Henry A. Waxman of California and Edward J. Markey of Massachusetts.

But on the domestic front, even some enthusiastic Obama supporters expressed disappointment that he had not used such an important global pulpit to make a stronger case for both international action and a forceful declaration of what the United States would do.

“We need President Obama to step up and say, ‘I need an economywide emissions cap,’ ” said Andrew Deutz, director of the Nature Conservancy’s international government relations program. “ ‘I need money to negotiate. I need Waxman-Markey passed by X date so I can go to Copenhagen and negotiate.’ ”

A few leaders did make significant commitments.

Prime Minister Yukio Hatoyama of Japan, who took office last week, said that his country would seek to cut greenhouse gas levels 25 percent, to 1990 levels, by 2020, and that Japan would provide significant financial and technical aid for green development.

Mohamed Nasheed, the president of Maldives, an Indian Ocean island state threatened with extinction if global warming causes seas to rise, said developing states should commit to mandatory limits. He said his country would commit to being carbon neutral by 2020.

Rajendra K. Pachauri, the chairman of the Intergovernmental Panel on Climate Change, warned that current emissions trajectories were speeding the world toward the panel’s worst-case possibilities.

“Science leaves us with no space for inaction now,” he said.   (link)