Fifty-five countries accounting for almost 80 percent of world greenhouse gas emissions have pledged varying goals for fighting climate change under a deadline in the ''Copenhagen Accord'', the United Nations said today.

''This represents an important invigoration of the UN climate change talks,'' Yvo de Boer, head of the UN Climate Change Secretariat, said of the national targets for curbs on emissions until 2020 submitted by January 31.

The countries, including top emitters led by China and the United States, mostly reiterated commitments unveiled before December's UN summit in Denmark, which disappointed many by failing to agree a tough, legally binding UN treaty.

De Boer said pledges covered 55 of 194 member nations and amounted to 78 per cent of emissions from energy use. The UN says the deadline is flexible and others can submit plans later.

''Greater ambition is required to meet the scale of the challenge,'' he said. ''But I see these pledges as clear signals of willingness to move negotiations towards a successful conclusion.'' Mexico will host the next annual UN meeting from November 29-December 10 as part of world efforts to avert more droughts, wildfires, floods, species extinctions and rising sea levels.

The Copenhagen Accord seeks to limit a rise in temperatures to below 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial levels and sets a goal of 100 billion dollars a year in aid for developing nations from 2020 to help confront climate change.

FILLING THE BLANKS It left blanks for countries to fill in climate targets for achieving the 2 C goal by January 31. Analysts say that the current targets will mean temperatures rise by more than 2 Celsius.

The 2020 goals include a European Union goal of a 20 per cent cut from 1990 levels, or 30 per cent if other nations step up actions. President Barack Obama plans a 17 per cent cut in US emissions from 2005 levels, or 4 per cent cut from 1990 levels.

But US legislation is bogged down in the US Senate.

China said it will ''endeavour'' to cut the amount of carbon produced per unit of economic output by 40 to 45 per cent by 2020 from 2005. The ''carbon intensity'' goal would let emissions keep rising, but more slowly than economic growth.

''Following a month of uncertainty, it is now clear that the Copenhagen Accord will support the world in moving forward to meaningful global action on climate change,'' said Jennifer Morgan of the World Resources Institute.

''However, although important in showing the intent to move to a low-carbon economy, the commitments are far below what is needed to avoid the worst impacts of climate change,'' she said.

And de Boer's statement did not even mention the Copenhagen Accord -- the main outcome of the low-ambition summit.

Originally worked out by the United States, China, India, Brazil and South Africa on December 18, the accord was not adopted as a formal UN pact after opposition from a handful of developing nations including Sudan, Venezuela and Cuba.

Today's statement only outlined 2020 pledges and did not say how many countries backed the deal -- the Copenhagen Accord is due to include a list of those who want to be ''associated'' with it. Submissions from some big developing countries such as China and India do not spell out if they want to be ''associated''.

Indian officials said they want the 1992 UN Climate Change Convention to remain the blueprint for global action, not the Copenhagen Accord.

South Korea's climate change ambassador Raekwon Chung said that US legislation was now vital.

''Every other country in the world is watching the US ...

If (US climate change legislation) does not happen this year, what will be the impact on the negotiations? I think the impact would be quite serious,'' he said.