A confession after more than 60 years came to light on Friday, as American President Barack Obama called his Guatemalan counterpart President Alvaro Colom apologizing for the experiment the US conducted in 1940s in which prisoners in Guatemala were infected with the diseases.

The US administration has finally confessed to carrying the tragic experiment in Guatemala during which thousands of Guatemalans were deliberately infected with sexually transmitted diseases.

The study was funded by the US National Institutes of Health into the affects of penicillin on Syphilis.

Guatemala had condemned the experiment as a crime against humanity and said it would study whether there were grounds to take the case to an international court.

"President Alvaro Colom considers these experiments crimes against humanity and Guatemala reserves the right to denounce them in an international court,"said a government statement.

The study, conducted from 1946 to 1948, deliberately infected some 1,500 Guatemalans with sexually transmitted diseases including Syphilis and Gonorrhea

Evidence was uncovered by Susan M. Reverby, a Wellesley College professor of history and women's studies, when she came across papers at the University of Pittsburgh archives detailing a study conducted in Tuskegee, Guatemala.