New York  - UN Secretary General Ban Ki-moon said that world leaders expressed a willingness to tackle climate change during a UN summit Tuesday but singled out industrial nations for not doing enough to reduce their own emissions.

Ban said the one-day summit at UN headquarters in New York had signaled "the determination of world leaders to address this challenge" and reach a "comprehensive" global treaty by a crucial Copenhagen summit set for December.

There was "a sense of optimism, urgency and hope that governments are determined to seal the deal in Copenhagen." Developing countries had shown willingness to contribute to lowering global emissions.

"Finally we are seeing a thaw in some of the frozen conditions that have prevented governments from making progress," Ban said of the summit, which featured speeches from more than 100 world leaders.

Most countries accepted the goal of preventing global temperatures from rising more than 2 degrees Celsius by 2050, Ban said, but the targets for each country to do its part have yet to be worked out.

Ban said industrial nations have set "inadequate" goals for themselves. Together they have pledged to cut greenhouse gas emissions about 20 per cent below 1990 levels by 2020.

Ban said they must agree to cut emissions 25-40 per cent by that time to address the worst effects of climate change. (dpa)