A lower Iranian court sentenced the priest, Yousef Nadarkhani, from the city of Rasht on the Black Sea, in December 2010 after finding him guilty of apostasy. He has been held for almost two years in Lakan prison and was arrested in October, 2009 while attempting to register his evangelical church in the city of Rasht.
The young priest was born to a Muslim family but denies he was ever a Muslim.
Under Iran's Sharia law, converting to another religion from Islam is apostasy, a crime punishable by death.
Churches are reported to have come under intense pressure in the last year, with a wave of random arrests and increasingly anti-Christian rhetoric.
In May, high profile Iranian cleric Ayatollah Mesbah Yadzi reportedly chided the authorities for failing to stem the growth of churches despite stepping up their efforts.
The ayatollah reportedly urged the government set up a central system to monitor and coordinate the suppression of churches.