Brazilian President Dilma Rousseff Friday vetoed parts of a new forestry code that environmentalists say would lead to further deforestation in the Amazon, home to the world's largest collection of plants and animals.

"The president of the Republic decided in favor of carrying out diverse vetoes and modifications to the draft law that deals with the forestry code," government lawyer Luis Inacio Adams told a news conference.

The overhaul of the 1965 forestry law approved by Congress a month ago had been seen as a victory for a powerful agri-business lobby after years of feuding with environmentalists.

But it is embarrassing for Brazil less than a month before it hosts the Rio+20 summit on sustainable development.

Rousseff removed 12 controversial articles and made 31 modifications to the bill which was to be published Monday in a special executive measure that enters into effect immediately, although it will have to be ratified later by the Congress.

Environment Minister Izabella Teixeira said that in vetoing parts of the bill the government was seeking to ensure that there was no loss of areas of the Amazon and protected sensitive ecosystems.

She said the government also acted to prevent amnesties for those who had illegally cleared areas in the past, to preserve small landowners, and hold timber producers responsible for protecting the environment.

The text to be published Monday maintains the obligation to protect 80 percent of the forest in rural areas of the Amazon and 35 percent of the sertao, or arid hinterland of northeastern Brazil.

But it eases restrictions for small landowners who face difficulties in recovering illegally cleared land.

The veto shows that Brazil "is a country determined to protect the environment while continuing to produce food," Texeira said.

But environmentalists who had pushed for a full veto were not pleased.

"Brazilian and world public opinion sees a country which continues to play with the future of its forests," said Maria Cecilia Wey de Brito, of the Brazilian branch of the conservation group WWF.

"We view the announcement of a partial veto with concern because we feel that a large part of the points most harmful for the environment have been maintained and only a few removed. In addition the veto will have to go through a Congress dominated by the agribusiness sector," said Raul do Vale of the Socioenvironmental institute (ISA).

On Thursday the government was handed a petition calling for a full veto with more than two million signatures collected online from dozens of countries.

The new law has provoked fierce clashes between environmentalists and supporters of farmers and ranchers over how to regulate the country's vast but vulnerable wilderness.

Brazil is a major beef and soybean producer, and with international crop prices high and in many cases rising, farmers are keen to cash in.

The bill approved by Congress a month ago defines what part of the forest landowners in the Amazon and other large ecosystems are responsible for protecting.

It shows the two faces of Brazil: on the one hand, a giant agricultural producer and exporter with nearly 28 percent of its territory under cultivation, and on the other an environmental powerhouse with forests covering 60 percent of its territory.

Agriculture Minister Jorge Alberto Mendes Ribeiro said the presidential veto ensured that the code reconciles the interests of both the environmentalists and the powerful agribusiness sector.

The decision comes only weeks before Brazil hopes to champion sustainable development at the June 20-22 Rio+20 summit that will be attended by 115 world leaders and 50,000 participants.