The world's biggest greenhouse gas polluters sent envoys to the US State Department in Washington DC today for discussions on climate change.
The two-day meeting, which is being attended by the United States and China, was called by President George W. Bush, whose administration has been criticised for not adopting mandatory limits for climate-warming emissions.
The White House favours "aspirational" targets.
By most counts, the United States is world's largest emitter of greenhouse gases, but at least one study this year indicated that fast-developing China is now in the lead.
Other participants in the talks are the European Union, France, Germany, Italy, the United Kingdom, Japan, Canada, India, Brazil, South Korea, Mexico, Russia, Australia, Indonesia and South Africa.
This gathering of major economies follows a high-level United Nations meeting on Monday that drew more than 80 heads of state and government to focus on the problem of global warming.
At its conclusion, Secretary-General Ban Ki-moon said he saw a "major political commitment" to seek a global solution to the problem at future UN discussions in December in Bali, Indonesia.
The Bali meeting in December is meant to begin figuring out a way to curb emissions after 2012, when the Kyoto Protocol expires.