BEIJING: Former US vice president Al Gore said Thursday China and the United States -- the world's biggest polluters -- should work on designing greener cities as part of their efforts to tackle climate change.

The Nobel Peace Prize winner told an urban development conference in Beijing that energy efficient buildings, low-emission vehicles, renewable energy resources and more trees in urban areas would help reduce pollution.

"We have to change our thinking and adopt a strategic approach and the United States and China could do no better than to focus on cities as the principle venue in which these changes can be made," Gore said.

As the world's leading economies and biggest polluters, China and the United States had "a special responsibility to address the world sustainability crisis," he said.

Gore congratulated China on its efforts to reduce its world-beating carbon emissions and invest in renewable energy, but said more needed to be done.

"China as well as the United States still need to do more, as every nation does," he said. "We have an opportunity in the development of cities and urban spaces to make tremendous progress."

China -- which in November admitted it is the world's biggest greenhouse gas emitter -- has some of the world's worst air pollution after rapid growth over the past 30 years triggered widespread environmental damage.

The country is undergoing an unprecedented urbanisation process as hundreds of millions of people head to fast-growing metropolitan areas.

To handle the massive influx of people, Beijing may need to invest up to 3.6 trillion dollars in urban infrastructure by 2020, state media said last year, citing a report by the state think-tank China Development Research Foundation.

China has started to build an "eco-city" near the northern port city of Tianjin and there are plans for dozens more around the country.

Authorities hope the development on 30 square kilometres of non-arable salt pans and former fishing villages will serve as an ultra-efficient alternative to ill-planned and heavily polluting mega-cities around the country.