Veteran evangelist Billy Graham has weighed in on the plight of imprisoned American Pastor Saeed Abedini.

Writing to President Hassan Rouhani, Graham said he has been watching Abedini's situation with "great concern."

Abedini is serving an eight year prison sentence in Iran. He was in Iran working to build an orphanage when he was arrested, with the primary reason being Abedini's Christian faith.

Sept. 26 was the one-year anniversary of Abedini's imprisonment. Graham, who wrote the letter earlier this week, wrote that, "Thousands will attend prayer vigils in more than 70 US cities, calling on your country to release this husband, father and servant of God. I join them by respectfully asking you to release Pastor Saeed Abedini from prison. Such an action would, I believe, have a positive impact in our nation, and might well be perceived by our leadership as a significant step in reducing tensions."

Graham said in the letter that as a religious leader he has often spoken about the need for greater understanding and peace among the nations of the world.

He continued, "As you come to the United States this week for the UN General Assembly in New York, it is my sincere hope that ways may be found to reduce the current tensions between the United States and the Islamic Republic of Iran."

Graham said that Monday's announcement of the freeing of 80 political prisoners was very encouraging.

However, Graham added, "I fear ... that the current publicity surrounding the continued imprisonment of Pastor Abedini, an American citizen, may further harm the already fragile relationship that presently exists between our two nations.

Releasing Abedini, Graham wrote, "would, I believe, have a positive impact in our nation, and might well be perceived by our leadership as a significant step in reducing tensions."