Hopes of securing a new international agreement to tackle climate change appear to have been scuppered, as major polluters, including Japan and China, have refused to cap their carbon emissions.

Leaders of the world’s major economies will meet in Copenhagen in December to sign a new treaty on climate change to replace the Kyoto Agreement.

In advance of that landmark meeting, thousands of climate experts gathered in Bonn last week to draft the skeleton of the Copenhagen deal.

But the discussions reached an impasse last Thursday when the Chinese delegation informed the conference that China would not sign up to mandatory caps on emissions, but was more likely to increase them.

‘‘China is still a developing country, and the present task confronting China is to develop its economy and alleviate poverty, as well as raise the living standard of its people,” said Qin Gang of the country’s foreign ministry, at a briefing in Beijing.

‘‘Given that it is natural for China to have some increase in its emissions, so it is not possible for China in that context to accept a binding or compulsory target.”

Japan, which ranks fifth among the world’s polluters, infuriated developing nations - including China and India - by announcing that it would aim to cut greenhouse gas emissions by just 15 per cent by 2020.

Its prime minister, Taro Aso, had been under pressure from international observers to set a far higher target, not least because emissions have risen 9 per cent since 1990.

Observers and activists pointed out that the 15 per cent goal would put Japan on target to reduce emissions by just 8 per cent between 1990 and 2020.T he move was pilloried by environmental groups and by developing nations, with Gang describing the target as ‘‘falling far short of .. . the aspirations of the international community’’.

The breakdown in talks will be particularly galling for the Obama administration, which had lobbied China intensively in the days before the Bonn conference. Todd Stern, Obama’s climate envoy, spent the early part of the week in Beijing, shuttling between diplomatic meetings and media engagements in an ultimately futile attempt to achieve consensus between what he called ‘‘the two gorillas in the room’’ in the climate change debate.

During his visit, he told the China Daily newspaper that the US ‘‘understands China’s paramount need to grow and develop for its people’’.

‘‘Our demand is that the development, with the available technologies, is based on low carbon growth,” he said.

But with China rejecting his overtures, the standoff makes it highly unlikely that any deal will be reached before the December talks.

‘‘I don’t think it is possible between now and the end of Copenhagen to finalise a long term response to climate change,” said Yvo de Boer, head of the UN Climate Change Secretariat.