New York, Sep 23 (DPA) World leaders committed to reaching a significant agreement to curb climate-damaging greenhouse gas emissions by the end of the year, but promised few specifics during the largest-ever summit on global warming.

The US and China, the world's two largest polluters, promised to tackle their own emissions and also tasked each other with doing more to halt the rise in global temperatures.

Chinese President Hu Jintao suggested his country could accept a target to slow its growth of emissions by 2020 but gave no specific figure. President Barack Obama spoke of a 'new day' and accepted responsibility for curbing US pollution but offered no new policies.

Newly elected Japanese Prime Minister Yukio Hatoyama made the most significant announcement, pledging to cut Japan's emissions by one quarter by 2020 in a sharp reversal from the previous governing party, which had been in power some five decades.

UN Secretary General Ban Ki-moon said he believed the summit, which featured more than 100 world leaders, had narrowed differences on reaching a global treaty. But he singled out industrial nations for not going far enough in reducing their own emissions.

Summing up the conference, Ban described 'a sense of optimism, urgency and hope that governments are determined to seal the deal in Copenhagen' at the December climate summit. Developing countries had also shown a 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 Tuesday.

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

Industrial nations have set 'inadequate' goals for themselves by pledging to cut greenhouse-gas emissions about 20 percent below 1990 levels by 2020. Ban said they must cut emissions by 25-40 percent by that time to stave off the worst effects of climate change.

Swedish Prime Minister Fredrik Reinfeldt, whose country holds the European Union presidency, warned that negotiations were 'close to a deadlock', yet he said there was no option but to push forward.

The EU has promised to cut its emissions 20 percent by 2020, but has offered to raise that to 30 percent if other countries follow suit in Copenhagen.

Smaller island nations again warned that their livelihoods would vanish if the world's major polluters couldn't reach a deal that stopped global temperatures - and sea levels - from rising.