KIGALI, Rwanda — Nations strove Friday for a deal to phase out hydrofluorocarbons from air conditioners and refrigerators as part of efforts to fight climate change. An agreement could put a half-degree Celsius dent in global warming by the end of the century, according to scientists.

At issue are greenhouse gases far more powerful than carbon dioxide. HFCs, as they’re known, were introduced in the 1980s as a substitute for ozone-depleting gases. But their danger has grown as air conditioner and refrigerator sales have soared in emerging economies like China and India. HFCs are also found in inhalers and insulating foams.

Major economies were still debating how fast to phase out HFCs, but hoped to reach a compromise by the end of the day. The United States and Western countries want quick action. Nations such as India don’t want to face reductions until possibly after 2030, giving their industries time to adjust.

Negotiators from dozens of governments are meeting in Rwanda, with U.S. Secretary of State John Kerry leading the American delegation.