Nearly 200 governments have agreed a faster timetable for phasing out chemicals that deplete the ozone layer and contribute to global warming.
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The schedule for eliminating hydrochlorofluorocarbons (HCFCs) comes forward by 10 years under the agreement signed at a UN meeting in Montreal.
HCFCs are used in applications such as refrigeration and fire-fighting.
A finance package to help developing countries switch technologies has yet to be agreed.
"It is perhaps the most important breakthrough in an international environment negotiation process for at least five or six years," said Achim Steiner, executive director of the UN Environment Programme (Unep).
"Governments had a golden opportunity to deal with the twin challenges of climate change and protecting the ozone layer, and governments took it."
Mr Steiner's comments came at the end of the week-long meeting which marked 20 years since the signing of the UN treaty regulating ozone-attacking chemicals, the Montreal Protocol.
Under the new deal, developing countries will phase out HCFC production and use by 2030, 10 years ahead of the previous target date.
They will also bring forward the date at which production and use must be frozen, from 2015 to 2013.
How this will be financed is not clear. A Unep statement says: "Governments agreed to commission a short study by experts to fully assess the likely costs of the acceleration."
Industrialised countries have so far spent more than $2bn (£1bn) to help developing nations clean up ozone-depleting installations.
Developed countries also face an accelerated timetable for phasing out HCFCs.
The Montreal Protocol was initially designed as a way of stopping destruction of the ozone layer, but in recent years it has become clear that it also provides a way of curbing global warming.
HCFCs and related chemicals such as hydrofluorocarbons (HFCs) are potent greenhouse gases.
The US administration says the new deal will be twice as effective as the Kyoto Protocol in controlling greenhouse gas emissions.