TORONTO — Governments of almost 200 countries have agreed to speed the elimination of a major greenhouse gas that depletes ozone, U.N. and Canadian officials said Saturday, describing a deal they said was a significant step toward fighting global warming.

The agreement reached Friday night will accelerate a treaty to freeze and phase out hydrochlorofluorocarbons (HCFCs) which are used in home appliances, some refrigerators, hair sprays and air conditioners, said Nick Nuttall, spokesman for the United Nations Environment Program.

"With this plan of an accelerated freeze and accelerated phase-out, we could have potentially significant benefits arising in terms of combating climate change and ozone loss," Nuttall said. "It's a remarkable change in how we view the issue of climate change."

The treaty known as the Montreal Protocol was originally established in the Canadian city in 1987 to protect the ozone layer from destructive chemicals. It was negotiated by 191 countries to cut back on chemicals blamed for destroying the ozone layer.

The member nations, gathering in Montreal again 20 years later, agreed to freeze production and consumption of HCFCs in 2013.

Developed countries have agreed to reduce production and consumption by 75 percent by 2010 and by 90 percent by 2015 with final phase out in 2020 — 10 years sooner than the earlier agreement. Developing countries have agreed to cut production and consumption by 10 per cent in 2015; by 35 percent by 2020 and by 67.5 percent by 2025 with a final phase-out in 2030.

In Washington, the White House said the agreement would cut in half the potential emissions of remaining chemicals harmful to the ozone.

"This action will not only speed up recovery of the ozone layer, but also represents one of the most significant new global actions to confront climate change by reducing the greenhouse gas profile of the phased-out substances," a White House statement said.

The final agreement is a combination of proposals by a number of countries, including the United States.

HCFCs emerged in the 1990s to phase out the older and more ozone-damaging chlorofluorocarbons (CFCs) used in air conditioners, refrigerators and hair sprays.

CFCs were blamed for a hole in the ozone layer, the atmospheric layer that helps protect against the sun's most harmful rays and traps the Earth's heat. The hole contributed to a rise in average surface temperatures.

However, while HCFCs are less destructive to the ozone layer, they are considered potent greenhouse gases that harm the climate — up to 10,000 times worse than carbon dioxide emissions.

U.N. climate experts said in a recent report that the atmosphere could be spared the equivalent of 1 billion tons of carbon dioxide emissions if countries used ammonia, hydrocarbons, carbon dioxide or other ozone-friendly chemicals, rather than HCFCs and hydrofluorocarbons or HFCs, in foams and refrigerants. Such alternatives are more common in Europe.

The White House said the quicker phase out was possible because of investments in technology.

"Faster healing of the ozone layer will help prevent human health damages cause by excess UV radiation, including skin cancer," it said.

It also said the agreement will spur development of new alternatives to these ozone depleting substances that have low or no greenhouse gas emissions.

Since the Montreal Protocol was signed in 1987, the White House said the U.S. has reduced by 90 percent the production and consumption of ozone-depleting substances. Worldwide, the Montreal Protocol has cut in half the amount of global warming caused by ozone-destroying chemicals that would have occurred by 2010, it said.

"The agreement to speed up the elimination of HCFCs will go down in the books as another successful chapter in the Montreal Protocol's proud and historic history (and) stand out as a pivotal moment in the international fight against global warming," John Baird, Canada's Environment Minister, said Saturday.

Governments also agreed to commission a short study by experts to fully assess the likely costs of the acceleration. The Montreal Protocol member nations will meet again at the United Nations in New York on Monday to further discuss climate change.