Assuring India and China that it wants their economies to grow, the US has told representatives of the world's leading economies that it is no longer 'absent without leave' in the global warming debate.

'As I have told my counterparts from China and India, we want your economies to grow. We want people to have a higher standard of living,' Secretary of State Hillary Clinton said, opening the first preparatory session of the Major Economies Forum on Energy and Climate Change here Monday.

'We just hope we can work together in a way to avoid the mistakes that we made that have created a large part of the problem that we face today,' she said, admitting the US role in spreading pollution.

Prime Minister Manmohan Singh's special envoy on climate change issues, Shyam Saran, is leading the Indian delegation to the gathering to set the stage for the forum leaders' meeting in July in Italy.

Climate change is 'an environmental issue, a health issue, an economic issue, an energy issue and a security issue', Clinton said, urging greater cooperation in advance of an international climate change conference to be held later this year.

'It is a threat that is global in scope but also local and national in impact...No issue we face today has broader long-term consequences or greater potential to alter the world for future generations.'

In addition to India, the US, the European Union and 14 other countries are participating in the preparatory session. These nations are Australia, Brazil, Canada, China, France, Germany, Indonesia, Italy, Japan, Korea, Mexico, Russia, South Africa and Britain.

A representative from Denmark is also attending because the country will host the UN conference on its climate change framework in December.

At the Copenhagen conference, leaders will discuss a new global agreement on greenhouse gas emission levels to replace the Kyoto Protocol, which expires in 2012.

'The United States is fully engaged and ready to lead and determined to make up for lost time, both at home and abroad,' Clinton said. 'We are back in the game. We don't doubt the urgency or the magnitude of the problem.'

She also highlighted the Obama administration's proposal for a broad, market-based cap on carbon pollution designed to help meet the goal of cutting national emissions 80 percent by 2050.

But international cooperation is needed to develop 'meaningful proposals to move the process forward,' she added. 'New policy and new technologies are needed to resolve this crisis.'

Ahead of the talks, environmental activists hung a large banner from a construction crane near the State Department with the message, 'Too Big to Fail: Stop Global Warming - Rescue the Planet.' Two protesters dangled from cords hung from the corners of the banner.