President Lula is set to make a formal announcement on 9 December
Twenty four years after the military left power in Brazil, the government is to create a Truth Commission to investigate crimes committed by the security forces between 1964 and 1985.
Brazil is the only country in Latin America which has not investigated deaths, disappearances and torture which took place during its dictatorship, or put alleged perpetrators on trial.
Although the number of victims is far smaller than those who died during military rule in neighbouring Argentina and Chile, nearly 500 people were killed or disappeared in Brazil. Thousands more were tortured, exiled or deprived of their political rights.
All attempts to bring people to justice have foundered on the blanket provisions of the 1979 Amnesty Law.
This not only authorised the release of political prisoners and the return of exiled opponents, but amnestied all political crimes and "connected crimes", which was understood to mean torture.
Now, just a year before he leaves office, President Luiz Inacio Lula da Silva has decided to set up a commission to investigate crimes committed during the dictatorship. Several of his ministers were themselves arrested and tortured by the military.
Paulo Sergio Pinheiro, Brazil's representative on the Inter-American Commission on Human Rights, said that President Lula would formally announce his decision on 9 December.
The terms of the truth commission, its members and its powers, are not yet known.
"Democracy cannot be consolidated unless the torture, disappearances and executions are faced and investigated," said Mr Pinheiro, who has also been UN rapporteur for human rights in Burundi and Burma.
President Lula's decision is believed to have been influenced by the decision of some of the victims' families to take their cases to the Inter-American Court of Justice.
The 1964 coup was bloodless but heralded two decades of military rule
Recently, government advertisements have appeared on TV appealing for anyone with information or documents about events during the dictatorship to come forward.
While some government files have been declassified, campaigners say the armed forces still hold other files that contain key information on the fate of those who disappeared.
Military chiefs deny this, saying all their files had been burned or destroyed.
Opinion in President Lula's coalition government is divided on the issue of pursuing those responsible for military-era crimes. While some ministers have said those who tortured and killed should be held to account, others are opposed to this.
Defence Minister Nelson Jobim has said the efforts by families and torture survivors to obtain justice amounted to "revenge".
The government recently extended the Secrecy Law, so that government files considered sensitive can be kept from public view for 60 years.
These contradictory signs indicate that the government's purpose in setting up a truth commission is far from clear, and therefore its results are uncertain.
For the families of the 140 Brazilians who disappeared during the dictatorship, the commission would be a final chance to find out what happened to them.
Laura Petit, now in her 60s, has spent the past 30 years searching for her sister and two brothers who were members of a rural guerrilla movement in the Amazon region of Araguaia in the early 1970s.
Sixty men and women of the Maoist-inspired Communist Party of Brazil disappeared after being surrounded and killed or captured by the army.
So far she has only found the remains of her sister.
"We want justice, it is our right," said Ms Petit.
For Suzana Lisboa, whose husband, a student leader, was tortured to death in prison, the commission will only be worthwhile if it has free access to the information in the archives.
"There can be no reconciliation without the recognition of what happened," she said.
Edson Teles, whose parents were tortured and killed during the dictatorship, believes that in revealing the past, the commission could avoid it being repeated.
Torture, he said, was still being practised in Brazil's police stations, with impunity.
Experts on truth commissions around the world, who met last week in Sao Paulo, said the success of the Brazilian initiative would depend on whether it was given the power to subpoena witnesses and access military files.
"There is a need to come to terms with these periods and not leave unfinished business," said Priscilla Hayner, director of the International Center for Transitional Justice in Geneva, who has studied all 45 such commissions.
"The right to know the truth is increasingly being recognised in international law."
Ms Hayner acknowledged that while Brazil has never had a truth commission, some steps had been taken.
A government committee has been paying compensation to people who suffered exile or imprisonment during the military regime, including President Lula himself.
Individual families have begun lawsuits against alleged torturers.
But many families remain scarred, still not knowing what happened to their relatives, nor why.
The family of Manoel Fiel Filho, a factory worker who was arrested and tortured to death in 1976, said they were only allowed to mourn him for a short while, in silence, before his coffin was taken to a cemetery and buried by strangers.
They were given no explanations and kept under constant surveillance.