Pope Benedict XVI has asked the Afghan president to show clemency towards a man facing possible execution for converting to Christianity.
Abdul Rahman was arrested earlier this month
Abdul Rahman has been charged with apostasy, a religious offence.
The Vatican said the pontiff had appealed to President Hamid Karzai to respect human rights guarantees enshrined in the Afghan constitution.
The Afghan government has been holding talks on the fate of Mr Rahman, who officials say "could be released soon".
Mr Rahman is on trial charged with rejecting Islam. He could be executed under Islamic Sharia law unless he reconverts.
'Understanding and respect'
The appeal was sent in a letter in Pope Benedict XVI's name by Vatican Secretary of State Cardinal Angelo Sodano.
The note, excerpts of which were released by the Vatican, said the pope's appeal was inspired by "profound human compassion" and by a "firm belief in the dignity of human life and by respect for every person's freedom of conscience and religion".
Releasing Mr Rahman would "contribute in a most significant way to our common mission to foster mutual understanding and respect among the world's different religions and cultures", it added.
The Afghan government has come under growing international pressure on the issue.
The US has urged President Karzai to seek a "favourable resolution" to the case.
Austria, current holder of the European Union's rotating presidency, said it would "leave no stone unturned" to protect Mr Rahman.