Yvo De Boer, executive secretary of the UN climate change secretariat, says China and India appear to be assuming leadership roles in the fight against greenhouse gas emissions. (AP Photo/World Economic Forum, Adam Nadel)

China is poised to join the European Union in claiming "front-runner" status among nations battling climate change, the UN's climate chief says.

In an interview with The Associated Press on Monday, Yvo de Boer said China is leaping ahead of the United States with domestic plans for more energy efficiency, renewable sources of power, cuts in vehicle pollution and closures of dirty plants.

"China and India have announced very ambitious national climate-change plans — in the case of China, so ambitious that it could well become the front-runner in the fight to address climate change," de Boer said. "The big question mark is the U.S."

Chinese President Hu Jintao will announce new plans to fight global warming when more than 100 world leaders attend a UN summit on climate change in New York on Tuesday, an event intended to rally momentum for crafting a new global climate pact at Copenhagen, Denmark in December.

China already has said it is seeking to draw 15 per cent of its energy from renewable sources by 2020.

U.S. President Barack Obama has been trying to build momentum for a new climate pact to succeed the 1997 Kyoto Protocol, which required mandatory cuts in atmospheric warming gases expires but expires at the end of 2012. His administration has announced a target of returning to 1990 levels of greenhouse emissions by 2020.

But with Congress moving slowly on a measure to curb emissions, the United States could soon find itself with little influence when 120 countries convene in Copenhagen.

Former U.S. president George W. Bush rejected the Kyoto accord based on its exclusion of major developing nations including China and India. China and the U.S. together account for about 40 per cent of all the world's emissions of carbon dioxide, methane and other industrial warming gases.

De Boer said he also was encouraged by Japan's new goal of a 25 per cent cut in greenhouse gas emissions from 1990 levels by 2020.