Story highlights Youcef Nadarkhani's next scheduled court date is September 8

He has been sentenced to death for leaving Islam

The House has passed a resolution condemning Iran for imprisoning him

Nadarkhani's case has galvanized American Christians

It has been more than 1,000 days since a Christian pastor was thrown into an Iranian jail for leaving Islam and sentenced to death for, as the U.S. State Department put it, "simply following his faith."

On Monday, the agency once again called on Iran to release Youcef Nadarkhani.

"Pastor Nadarkhani still faces the threat of execution for simply following his faith, and we repeat our call for Iranian authorities to release him immediately," said a statement from State Department spokeswoman Victoria Nuland.

His next scheduled court date is September 8.

Nadarkhani, born to Muslim parents in the northern Iranian town of Rasht, converted to Christianity when he was 19.

Later he was ordained as a minister and led a network of house churches in Iran.

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He was arrested in October 2009 after he lodged a protest with local education officials after learning his child was being forced to read from the Quran, the Muslim holy book, in school.

He was charged with apostasy and convicted in a provincial court -- which sentenced him to death.

He appealed, and during a trial in a lower court, refused to recant his beliefs.

The case made its way to the Supreme Court, which said Nadarkhani's sentence could be overturned if he recanted. The 34-year-old pastor has refused.

Even though the constitution of Iran -- a predominantly Shiite Muslim country -- guarantees equality to members of religious minorities, that has not been the case in practice.

And while apostasy is not an offense codified in Iranian law, converts from Islam often face the death penalty, Amnesty International said.

Persecution has increased since Iran's disputed presidential election in 2009, with Baha'is, Christian converts and even Sunni Muslims bearing the brunt.

In April 2010, the U.S. Commission on International Religious Freedom reported a rise in church raids and harassment of worshippers by Iranian authorities.

And Amnesty International, in a report released earlier this year , said "repeated calls by the Supreme Leader and other authorities to combat "false beliefs" -- apparently an allusion to evangelical Christianity, Baha'ism and Sufism -- appear to have led to an increase in religious persecution."

In February, the White House issued a pointed statement in the Nadarkhani case, strongly condemning the reports of an execution order.

"This action is yet another shocking breach of Iran's international obligations, its own constitution, and stated religious values," the statement said. "The United States stands in solidarity with Pastor Nadarkhani, his family, and all those who seek to practice their religion without fear of persecution -- a fundamental and universal human right. "

From small churches to large organizations, Nadarkhani's case has galvanized American Christians.

The Voice of the Martyrs , an organization that monitors and attempts to assist with persecuted and minority churches around the world, has closely followed Nadarkhani's case and other developments involving Christians in Iran.

But the issue has not been solely spearheaded by Christian groups; Muslim organizations have also been vocal about condemning Iran.

"These types of cases, especially around apostasy, are too frequent occurrences in the Muslim world and as a Muslim, I am appalled," said Harris Zafar, national spokesman for the Ahmadiyya Muslim Community . "To do this in the name of Islam, I know that this isn't Islam. It is a violation of human rights and it is a violation of Islam."

The American Center for Law and Justice -- a group "specifically dedicated to the ideal that religious freedom and freedom of speech are inalienable, God-given rights" -- was asked by the pastor's lawyers last year to help publicize Nadarkhani's case, according to Jodran Sekulow, executive director of the group.

Since that time, Sekulow has been in somewhat regular contact with the pastor's legal team and the ACLJ have organized a Twitter campaign called " Tweet for Youcef ."

The group says the campaign is now reaching more than 2.5 million Twitter accounts in 234 countries and territories around the globe each day.

In March, the U.S. House of Representatives passed on a 417-1 vote a resolution condemning Iran for imprisoning Nadarkhani, while calling for his immediate release.

In a letter posted May 30 on Voice of the Martyrs website, Nadarkhani seemed a bit taken aback by all the attention his case was garnering and by those using it for political purposes.

"I want to appreciate all those (who) are trying to reach this goal," he said. "At the end I hope my freedom will be prepared as soon as possible ..."