Activists on Thursday said they handed Brazil's president a petition with nearly two million signatures urging her to veto a new forestry code that could result in increased Amazon rainforest deforestation.

The bill would open huge areas of the country to farming if they were illegally logged before July 2008, and would allow farming along environmentally sensitive riverbanks.

President Dilma Rousseff has until Friday, less than one month before the Rio+20 UN summit on sustainable development, to veto the controversial measure.

The bill has support from Brazil's powerful agribusiness sector.

Avaaz, a global activist group concerned with issues of climate change, human rights and poverty, said the government was handed a petition with nearly two million signatures collected online from dozens of countries.

"Veto everything, Dilma," said more than 150 environmental groups and several other representatives of Brazil's Bar Association, the Catholic Church, small farmers as well as politicians and even former environment ministers.

Avaaz spokeswoman Regina Tavini said Rousseff however did not receive the petitioners.

The activists called for a festive vigil from late Thursday until the president announces her decision.

The bill was initially intended as a bid to rein in unfettered logging and increase protection of Brazil's forested areas, which play a key role in reducing greenhouse gases.

But farm-based economic interests prevailed, and the bill was reshaped to ease restrictions that have been in place since 1965 and are credited with curbing deforestation.

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.

A government source said Rousseff plans to veto part of the bill approved by Congress a month ago, removing any amnesty for those who logged illegally in the past and restoring protection of environmentally sensitive areas such as riverbanks.

More than 60 percent of Brazil's 8.5 million square kilometers (3.3 million square miles) are jungles and forests, but two thirds of it is either privately owned or its ownership is undefined.

In the sprawling Amazon River basin region, the existing law requires that as much as 80 percent be kept as woodland.

The proposed reform threatens 690,000 square kilometers (some 266,000 square miles) of vegetation, which would prevent Brazil from reaching its goal of reducing deforestation by 80 percent, according to Climate Observatory, a network of 26 groups set up in 2002 to promote civil society participation on climate change issues.