Argentina is collecting blood samples taken from relatives of people who disappeared during the country's military dictatorship from 1976-1983.
It is hoped the samples will allow identification now and in the future
Officials plan to collect some 3,600 specimens which will be sent to the US.
Officials hope DNA from the blood will help identify about 600 bodies which have been found in recent years.
Up to 30,000 people are said to have been killed or disappeared in Argentina's "dirty war" when the military regime persecuted opponents.
Human rights groups say that the DNA gathering plan would allow aging relatives to play a vital part in the hunt for the missing, even after they die themselves.
"Part of the anguish one perceives from the mothers and the fathers of the disappeared is that they may die and fear that could hinder the identification process," Eduardo Luis Duhalde, Argentina's human rights secretary, said.
"This project will try to bring them some peace, so they can know that, although they may no longer be here physically, elements will exist allowing us to identify whatever remains are found," Mr Duhalde added.
The scheme is the latest in a series of moves by the government of Nestor Kirchner to try to deal with the events of the military era.
This week the Argentine navy formally handed possession to human rights groups of one of the most notorious buildings used during military rule.
The Naval Mechanics School in the capital, Buenos Aires, in which an estimated 5,000 people were tortured and killed, will now be turned into a memorial museum.
In 2005 Argentina's Supreme Court ruled that amnesty laws protecting former military officers from misdeeds committed during that era were unconstitutional, paving the way for possible prosecution.
Military officers who carried out the human rights abuses were granted immunity from prosecution in Argentina under laws passed soon after the return to democracy.