A deal by 191 nations to eliminate ozone-depleting substances 10 years ahead of schedule is a 'pivotal moment' in the fight against global warming, Canadian Environment Minister John Baird said.

Delegates at a UN conference in Montreal struck the deal late on Friday. The agreement will phase out production and use of hydrochlorofluorocarbons (HCFCs) for developed countries to 2020 from 2030 and to 2030 from 2040 for developing nations.

The UN also hailed the deal, saying it could cut billions of tones in greenhouse gas emissions.

Washington says the faster phase-out of HCFCs will be twice as effective as the Kyoto protocol in fighting climate change. The US walked away from the protocol in 2001 and Canada says it cannot meet its Kyoto targets.

'It (the deal) ... will stand out as a pivotal moment in the international fight against global warming,' Baird told a televised news conference in Montreal.

Baird said the fact that India, the US and China -- major countries not bound by firm Kyoto targets -- had signed the deal was a promising sign ahead of talks designed to produce a climate change accord after 2012.

The UN Environment Program (UNEP) conference in Montreal marked the 20th anniversary of the Montreal protocol, which was designed to cut the use and output of chemicals found to harm the ozone layer.

Damage to the layer protecting the Earth from ultraviolet radiation has been linked to an increased risk of cancers and cataracts among humans. HCFCs are used in air conditioners and refrigerators.

'Governments had a golden opportunity to deal with the twin challenges of climate change and protecting the ozone layer and governments took it,' Achim Steiner, UNEP's executive director, said in a statement.

'The precise and final savings in terms of greenhouse gas emissions could amount to several billions of tones.'

White House spokeswoman Dana Perino said the agreement 'represents one of the most significant new global actions to confront climate change by reducing the greenhouse gas profile of the phased-out substances”.

Under the terms of the deal, all governments agreed to freeze HCFC production by 2013 compared to average production levels in 2009 and 2010.

Developed nations agreed to cut production and consumption by 75 per cent by 2010 and by 90 per cent by 2015 on the way to a full phase-out by 2020.

Developing nations committed to a 10-per cent cut in production and consumption by 2015, a 35-per cent cut by 2020, a 67.5-per cent reduction by 2025 and a phase-out by 2030.

UNEP said that delegates had agreed to find enough money to provide financial and technical help to developing nations, but gave no details. The US said before the talks that finding enough aid to satisfy China would be crucial.

Baird said he had been 'stunned and really pleased' by what he called China's huge contribution during the talks.

UNEP said it has spent $2 billion US since 1987 on helping developing nations curb the use and production of ozone-damaging substances.

A study group will now probe how much the accelerated elimination is likely to cost. It will report early next year.Reuters