Bush declined to sign the Kyoto protocol to cut global emissions in 2001, saying it unfairly exempted developing nations from targets.

Heat-trapping carbon gases are almost certainly linked to rising world temperatures, according to a new report released by global climate scientists. The United States emits more carbon gases than any other nation by burning fossil fuels like oil and coal.

Big developing nations are also serious polluters but Brazil is an exception because half its territory is covered by Amazon rainforest and because it uses hydropower and renewable sugar-cane ethanol for fuel.

US leaders want Brazil's cooperation as they try to develop a market for corn-derived ethanol to ease dependence on oil and on oil-producing nations like Venezuela and Iran, a senior State Department official said during a visit to Brazil last week.

Brazil has been eager to jump on the bandwagon because cane producers want to create more foreign demand for their cheaper, more efficient cane ethanol.

"We are doing our part," Lula said. "We must demand that rich countries, which are responsible for 70 percent of the global carbon gases emitted, reduce their pollution."

The United States charges steep tariffs on imports of Brazilian ethanol, and Brazil has struggled to export elsewhere because so far it is the only reliable producer of the fuel.