Cattle ranching is blamed for up to 70% of current Amazon deforestation
Norway has pledged $1bn (£500m) to a new international fund to help Brazil protect the Amazon rainforest.
The donation is the first to the fund which Brazil hopes will raise $21bn to protect Amazon nature reserves.
Norway's prime minister said the project was important in the fight to reduce global warming.
Brazil is one of the world's biggest greenhouse gas emitters, with three-quarters of its total coming from the burning of trees in the Amazon.
The money will be released over seven years to promote alternatives to forest-clearing for people living in the Amazon, and support conservation and sustainable development.
Norwegian prime minister Jens Stoltenberg said: "Efforts against deforestation may give us the largest, quickest and cheapest reductions in greenhouse gas emissions.
The Amazon rainforest
Largest continuous tropical forest
Shared by nine countries
65% Brazilian territory
Covers 6.6m sq km in total
Pop: 30m - 23.5m are in Brazil
"Brazilian efforts against deforestation are therefore of vital importance if we shall succeed in our campaign against global warming," he added.
The Brazilian government wants to raise $21bn through foreign donors by 2021, although President Luis Inacio Lula da Silva has insisted that the Amazon's preservation is Brazil's responsibility.
He welcomed Norway's pledge, saying: "The day that every developed country has the same attitude as Norway, we'll certainly begin to trust that global warming can be diminished."
Japan, Sweden, Germany, South Korea and Switzerland are said to be considering donating to the fund, which was launched last month.