The United States and China announced Friday they would seek to eliminate some of the world's most potent greenhouse gases through the 1987 Montreal Protocol, the landmark treaty that successfully phased out ozone-depleting substances decades ago.

The move, announced at the Group of 20 summit in St. Petersburg, is significant because it provides a clear path for curbing a major contributor to global warming in the near term as world leaders grapple with the more challenging task of cutting carbon dioxide in the coming decades.

President Barack Obama and Chinese President Xi Jinping said they would work to phase out hydrofluorocarbons (HFCs) — a class of chemicals commonly used in refrigerators and air conditioners — through the Montreal Protocol, even as they tried to make progress through the annual climate talks held by the United Nations. The U.N. Framework Convention on Climate Change has yet to produce a broad, binding, global warming accord that many scientists say would be needed to limit the world's growing carbon output. Other G-20 leaders also endorsed the approach Friday in a joint statement.

Durwood Zaelke, president of the nonprofit Institute for Governance & Sustainable Development, called HFCs "the biggest climate prize available to the world in the next few years."

In an email, Zaelke estimated that the accord could cut the equivalent of 100 billion tons of carbon dioxide by 2050 and would avoid up to nearly 1 degree in global warming.

"This high-level agreement during the G-20 in St. Petersburg shows how effective climate policy can be when it's done at the leader level," he wrote.