The UN has received pledges from 55 countries, accounting for 78 per cent of global emissions, to cut their share of greenhouse gases by 2050, a development welcomed by the world body as an "important invigoration" to the Copenhagen climate talks.
Some of the world's biggest polluters, the US, China, European Union and India, have reiterated their previous pledges of cutting emissions by 2020 that were widely regarded as weak, especially the 17 per cent reduction of carbon emissions from 2020 levels proposed by the US.
Experts have noted that the current pledges are not sufficient to meet the goal set to limit global temperature rise to two degree Celsius.
But the UN welcomed these countries joining the Copenhagen Accord, the agreement that was produced following the climate talks in the Danish capital in December.
"The commitment to confront climate change at the highest level is beyond doubt," said UN's Climate Chief Yvo de Boer, noting that the pledges represented an "important invigoration" of the discussions at Copenhagen.
"Greater ambition is required to meet the scale of the challenge. But I see these pledges as clear signals of willingness to move negotiations towards a successful conclusion," he added.