Environmentalists and small farmers marched outside the National Congress Wednesday to urge President Dilma Rousseff to veto changes to the country's forestry code they fear will accelerate deforestation of the Amazon rainforest.

The bill, which is backed by the powerful agribusiness sector, would allow huge areas of the country to be farmed if they were illegally logged before July 2008, and would allow farming along environmentally sensitive riverbanks.

It was initially intended as a bid to rein in unfettered logging, and increase protections 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.

"We hope that the president will show good sense with respect to the environment, even if it goes against the wishes of major agribusiness producers," said Adson Lima, a member of a mangrove protection non-governmental organization, as he protested outside Congress. Lima wore a t-shirt that read "Slap your veto, Dilma Veto."

"The interests of deputies and agribusiness will destroy nature and harm our people," added Sandro Potiguara, a member of the Potiguara indigenous group of northeast Brazil.

During her 2010 election campaign Rousseff pledged to reject the legislation, which critics said encouraged deforestation.

The new Forestry Code, which was already approved in the Senate, is to be submitted to the lower house of Congress next week after two years of debate. If approved, president Rousseff would then sign the measure for it to become law.

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.