TIANJIN, China: China on Tuesday told the United States and other rich nations to "dramatically" improve their greenhouse gas emission targets, as it blamed them for gridlock in UN climate change talks.

Delegates from more than 170 countries are in the northern Chinese city of Tianjin this week in an effort to break the stalemate in long-running United Nations negotiations aimed at forging a deal on global warming.

Chief China negotiator Su Wei told reporters that the actions of rich nations should be in focus in Tianjin and the major UN summit on climate change in Cancun, Mexico, next month.

"Many of the developed countries, especially a handful of them, have been very laggard on climate change actions and this has led to failure of major breakthroughs or progress in the negotiations," Su said.

Europe has pledged to cut its emissions of the greenhouse gases blamed for global warming 20 percent by 2020, based on 1990 levels.

The United States has pledged a 17 percent reduction from 2005 levels.

But Su said these targets were not good enough.

"We believe it is a positive thing that they put forward these targets, but these targets are still far away from the expectations of developing countries and from what is demanded by science," Su said.

"Therefore the emissions reduction goals of developed countries should be dramatically increased."

Su said China wanted the targets to be discussed as part of the negotiations for Cancun.

Rich industrialised countries and fast-growing developing nations have long tussled over who should carry the greatest burden for reducing greenhouse gases such as carbon dioxide.

The issue was one of the main reasons for the failure by world leaders to forge a comprehensive and binding deal on fighting climate change in Copenhagen last year.

At Copenhagen the world leaders agreed on a goal of limiting global temperature rises to two degrees Centigrade (3.6 degrees Fahrenheit).

However there was no agreement on how this would be done and by when.

Scientists say countries have to act quickly to curb greenhouse gases and stop rising temperatures that could lead to catastrophic weather such as droughts and floods.