Argentine Plaza de Mayo activists lobby Pope Francis
Argentine activists searching for missing victims of the Dirty War have met Pope Francis, who was a priest in Argentina during military rule.
The Grandmothers of the Plazo de Mayo group asked the Pope to open Vatican archives from the 1976-1983 period.
The activists are trying to trace hundreds of babies that were snatched from political prisoners.
The group's leader Estela de Carlotto said the Church must know where some of the children were taken.
She met the Pope during a general audience at the Vatican, and handed him a letter asking for the archives to be open.
"Every detail can help to identify those who were taken from our families," the letter read.
She said the Pope had told her: "You can count on me. You can count on us."
Vatican archives are generally not opened for many decades.
Argentina's bishops have already issued an apology for the Church's failures to protect its members during the military dictatorship.
The Grandmothers of the Plazo de Mayo group estimates between 400 and 500 children were taken from their mothers and given to families who supported the regime.
More than 100 children given for adoption to military or police couples have been reunited with their biological families.
However, some of the children have said they would rather not know their origins, especially if the information implicates their adoptive parents in illegal acts.
Two of the junta's leaders were jailed in 2012 for the systematic theft of babies.
Human rights groups say some 30,000 people were killed or disappeared by the military regime.