Cattle graze in a deforested farm in the northern city of Presidente Figueiredo, Brazil, Thursday, Sept. 20, 2007. New studies suggest the Amazon may be approaching a tipping point, at which the drier conditions caused by deforestation will reduce rainfall enough to transform the humid tropical forest into a giant savanna. (AP Photo/Andre Penner)

The promised donation is the first to a new Amazon preservation fund Brazilian officials hope will raise US$21 billion to protect nature reserves, to persuade loggers and farmers to stop destroying trees and to finance scientific and technological projects.

``Efforts against deforestation may give us the largest, quickest and cheapest reductions in greenhouse gas emissions,'' Stoltenberg told reporters. ``Brazilian efforts against deforestation are therefore of vital importance if we shall succeed in our campaign against global warming.''

Amazon trees are felled by loggers or burned in bulk, releasing an estimated 400 million tons of carbon dioxide _ 80 percent of Brazil's greenhouse gases _ into the atmosphere every year and making the country one of the world's top sources of emissions.

Brazil slowed Amazon jungle clearing between 2005 and 2007, but environmentalists worry the trend may now reverse itself, as more trees are cut to make way for cattle ranches and soy plantations that soaring world food prices have made more profitable.

Norway will give Brazil US$21 million this year and $210 million next year, but plans to donate the full US$1 billion only ``we are able to see a clear documentation that deforestation is being reduced,'' Stoltenberg said.

He added that Norway will use Brazil's annual statistics on deforestation to determine how much money to release, although Norway plans to develop better systems to track deforestation _ a task now complicated by clouds that hang over the jungle for much of the year.

``The day that every developed country has the same attitude as Norway, we'll certainly begin to trust that global warming can be diminished,'' said Brazilian President Luiz Inacio Lula da Silva.

Environment Minister Carlos Minc said Japan, Sweden, Germany, South Korea and Switzerland are considering donating to the fund, which Silva created by decree in August.

The donations will be key to a new development model for the impoverished Amazon region, which covers nearly 60 percent of Brazil, Minc added.

The Amazon loses the equivalent of one-and-a-half football fields of forest every minute to logging, ranching and farming, the Brazilian environmental group Imazon has estimated. About 20 percent of the forest, which covers an area larger than Western Europe, has been destroyed.