President Barack Obama and Chinese President Xi Jinping, left, walk at the Annenberg Retreat of the Sunnylands estate Saturday, June 8, 2013, in Rancho Mirage, Calif. (Evan Vucci/AP)

The agreement between President Obama and Chinese President Xi Jinping on Saturday to wind down the production and consumption of a class of chemicals commonly used in refrigerators and air conditioners could mark a key step toward eliminating some of the most potent greenhouse gases.

The United States and roughly 100 other countries have already pledged to seek substitutes.

For the first time, the United States and China will work together to persuade other countries, most notably holdouts such as Brazil and India, to join the effort to slash or eliminate the use of hydrofluorocarbons, or HFCs.

The chemical group currently accounts for only 2 percent of greenhouse gases, but consumption is growing exponentially as people in developing countries grow wealthy enough to purchase air conditioners. A global push to get rid of HFCs could potentially reduce the greenhouse gases by the equivalent of 90 gigatons of carbon dioxide by 2050, equal to roughly two years’ worth of current global greenhouse gas emissions, experts estimate.

Obama and Xi said they would use the framework of the Montreal Protocol, established in 1987 to combat the use of chemicals that were depleting stratospheric ozone. The Montreal Protocol succeeded in phasing out nearly 100 chemicals, but one unforeseen side effect was to spur the production of HFCs, which are short-lived and do not damage the ozone but are hundreds to tens of thousands times more potent greenhouse gases than carbon dioxide.

Left unabated, HFC emissions could grow to nearly 20 percent of carbon dioxide emissions by 2050, a serious climate mitigation concern, the White House said. The United States, China and Japan are the biggest consumers.

“This is a big deal,” said John Podesta, chairman of the Center for American Progress, a liberal-leaning think tank. “Obama deserves a lot of credit for this. He said he would tackle climate change, and this is really an important achievement.” He said experts at the think tank estimated that it could shave 0.5 degrees Celsius from the projected increase in global temperatures by the end of the century.

“The China-U.S. agreement on phasing down HFCs under the Montreal Protocol will provide the single biggest, fastest, cheapest, and most secure piece of climate mitigation available to the world through 2020,” said Durwood Zaelke, president of the Institute for Governance & Sustainable Development and a longtime advocate of fast-action mitigation under the Montreal Protocol.

HFCs, unlike other pollutants, are manufactured by humans and not found in nature. In addition to being used as refrigerants, they are used in insulating foams, solvents and aerosol products. There are substitutes in some applications, such as automobile air conditioners, but many substitutes are not available yet.

Although the issue of HFCs has been on the table for the past four years, the agreement by China to wind down HFC use came together over the past week as the two sides prepared for the summit between Xi and Obama. On the Chinese side, the powerful National Development and Reform Commission played a key role while working with the White House and international climate negotiators from the State Department.

Much work remains, however. About 30 countries have not agreed to, as the administration put it, “phase down” HFCs. But China, the biggest market, has been considered the key to persuading others, administration officials said.

“India will still be unhappy. This isn’t done tomorrow,” said one administration official. “But the fact that China moved in this way will have a huge impact on this whole discussion.”

It might also signal a move in China, where an extreme bout of air pollution in Beijing and other major cities last winter triggered widespread calls for action to reverse the tide of environmental degradation.

Juliet Eilperin contributed to this report.