The president and Mr. Zhang met briefly at the summit meeting on Tuesday, before Mr. Obama’s speech. In his remarks, Mr. Obama said he had pressed Mr. Zhang on the urgency for both countries to take the lead, and noted that he and the Chinese president had already reached an accord to cut the use of hydrofluorocarbons, a potent category of greenhouse gases.

The United States, he said, would meet a pledge to reduce its carbon emissions by 17 percent, from 2005 levels, by 2020 — a goal that is in large part expected to be met through the proposed E.P.A. regulation. Now, Mr. Obama said, the United States is preparing ambitious new targets to cut emissions further by 2050, with specifics to be made public ahead of a climate summit meeting in Paris in 2015. Other nations are expected to submit their own plans.

With its surging use of coal, China has overtaken the United States as the world’s largest greenhouse gas polluter. But in the past year, as thousands of Chinese have protested the reliance on coal and its contribution to some of the world’s dirtiest air, Chinese authorities have signaled that they intend to adopt policies to reduce the use of coal.

“We’ve been working hard on this plan, looking at what kind of changes we will make to industry,” Li Junfeng, director general of China’s National Center for Climate Change Strategy, said in an interview.

Image President Obama before speaking Tuesday at the United Nations General Assembly, where he urged more than 100 world leaders to confront climate change. Credit... Damon Winter/The New York Times

Mr. Li said that his center had prepared “multiple choice” options for a proposed climate plan, and that Beijing would choose one to put forth based on the perceived stringency of the American plan for emissions cuts by 2050.

In recent years, the Chinese government has sent other signals about addressing carbon pollution, some of them encouraging to environmental experts. It has created seven regional cap-and-trade plans aimed at cutting carbon pollution from coal plants, and in August, a Chinese government official suggested that China was exploring the possibility of a national cap-and-trade plan.