U.S. Secretary of State John Kerry has called on Iran to release Iranian-American pastor Saeed Abedini.

In a statement posted on the State Department website, Kerry is asking Iran to "work cooperatively" to help Abedini and two other Americans return to their families.

In his strongest statement to date, the Secretary of State noted that Abedini will have been in detention for one year on September 26. He is serving an eight-year prison sentence.

The United States has asked Iran to work cooperatively to help U.S. citizens Robert Levinson, Amir Hekmati, and Saeed Abedini to return to their families after lengthy detentions.

"We urge the Iranian Government to release Mr. Hekmati and Mr. Abedini and to help us locate Mr. Levinson so that they may be reunited with their families as safely and as soon as possible," said the statement on the State Department website.

Iran has said Abedini is a national security threat. The pastor's family, however, have campaigned on his behalf, noting the he is being jailed because of his Christian faith.

The appeal by Kerry, who criticized Iran in March for holding Abedini, comes on the heels of a denial of his legal appeal by a Tehran court.

The pastor's wife Nagmeh Abedini called the decision "devastating", according to the American Center for Law and Justice (ACLJ). The group has been representing her and their two children in the case.

In a statement on August 26, the ACLJ said it was exploring all legal and governmental options available.

"While we remained hopeful that Iran would use its own appeal process to finally show respect for Pastor Saeed's basic human rights, again Iran has demonstrated an utter disregard for the fundamentals of human rights," said Jordan Sekulow, the ACLJ's executive director.

"We are exploring all options with Pastor Saeed 's family, including options in this country and abroad to bring more pressure on Iran from the U.S. and other countries around the world. The decision is deeply troubling and underscores Iran's continued violation of principles of freedom of religion, association, peaceful assembly, and expression."

In the same post on the ACLJ website, Nagmeh Abedini had expressed her disappointment in the U.S. government's efforts on her husband's behalf.

" I am disappointed that as a country that was founded on religious freedom, our government has been awkwardly silent as an American citizen is wasting away in an Iranian prison because he chose to practice his God-given right to choose his religion," she said.

"My husband is serving 8 years in the notorious Evin prison and facing daily threats and abuse by radicals because he refuses to deny his Christian faith. And yet, my President, President Obama, has not spoken a word about him."

The ACLJ called Kerry's remarks an important step and Abedini's wife expressed her thanks to Kerry, while still criticizing Obama for his silence.

"President Obama must demonstrate that America will not stay silent in the face of religious persecution, nor will it let an American citizen waste away in an Iranian prison simply because he chose to follow Jesus," she said.

Abedini's Iranian family was allowed to see him earlier this month. The ACLJ reported at that time that the pastor was suffering severe pain from the beatings he has received at Teheran's Evin Prison.