"We will fully comply with the targets. It doesn't matter that Copenhagen didn't go as well as we had hoped," Environment Minister Carlos Minc told reporters after meeting with President Luiz Inacio Lula da Silva.
Lula will veto three items from a climate bill approved by Congress in November but would maintain the emissions targets, Minc said.
"The targets were maintained, which is the most important. Brazil will have a strong climate change policy," he said.
Brazil aims to reduce its projected 2020 greenhouse gas emissions by as much 39 percent. That amounts roughly to a 20 percent reduction from 2005 levels.
According to the bill that has become law, those targets will be quantifiable and verifiable.
Latin America's largest country had tried to prod other developing and industrialized countries into adopting bold targets at the UN climate summit in Copenhagen earlier this month. But the meeting failed to produce a new framework agreement on climate to follow the Kyoto Protocol which expires in 2012.
Brazil is one of the largest carbon emitters, largely due to the destruction of the Amazon rain forest. Deforestation, which has fallen sharply in recent years, releases carbon as trees burn or decompose.
Among the items Lula will veto were proposals to limit the construction of small hydroelectric plants and reduce the use of fossil fuels.