Yousef Nadarkhani was arrested in 2009 and found guilty of apostasy. He was sentenced to death and has been in prison ever since, awaiting the outcome of a lengthy appeal process.
He was reportedly given the option of renouncing his faith in order to have the charges annulled and the death sentence lifted, but he refused.
There are fears that the pastor could be executed at any time after unconfirmed reports emerged last month that the Iranian authorities had given the green light for his execution.
Christian Solidarity Worldwide launched a month of prayer last week in the run-up to the pastor’s 35th birthday on 12 April.
The organisation, which supports persecuted Christians, said it was not uncommon for Iranian authorities to carry out executions without warning and announce them only after they have been carried out.
CSW’s month of prayer is being supported by the World Evangelical Alliance (WEA).
Godfrey Yogarajah, Executive Director of the WEA’s Religious Liberty Commission said: “In Acts 12, we read of Peter’s miraculous release from prison while the church was earnestly praying for him.
“We have a vital role to play by standing in solidarity with Pastor Nadarkhani and praying a lifting of the death sentence, and for his unconditional release.”