Two Christian pastors from South Sudan who traveled north to Sudan and were arrested on charges of spying could face the death penalty when their trial begins next week, according to their attorneys.

“I’m fearful that they will execute these pastors for practicing their faith."

- David Curry, CEO of Open Doors USA

Yat Michael Ruot and Peter Yein Reith, both Presbyterian pastors from the breakaway Christian nation of South Sudan, are being held by Sudan’s National Intelligence and Security Services on charges of undermining the constitution and espionage. Their supporters say their arrest and pending trial is just the latest effort by the militant Islamist government in Khartoum to stamp out Christianity.

“I’m fearful that they will execute these pastors for practicing their faith,” said David Curry, CEO of Open Doors USA, a group dedicated to advocating for the victims of Christian persecution.

The pair also was charged with “inciting organized groups” and “offending Islamic beliefs,” which call for imprisonment.

The trial was set to begin Tuesday, but was postponed to May 31.

Ruot, who is from Juba, the capital city of South Sudan, was arrested Dec. 21 after he delivered a Sunday sermon in Omdurman, a Sudanese city across the Nile from Khartoum. Reith, who, like Ruot, is from the Presbyterian Evangelical Church, was arrested Jan. 11 when he was called in by security services and taken into custody. His supporters believe his arrest was prompted by a letter he wrote to the Office of Religious Affairs in Khartoum inquiring about Ruot.

Their whereabouts where unknown for months following arrest, which is in violation of international human rights laws. But a month ago, they were taken from Khartoum’s police station to a detention center, according to Ruot’s wife. Charges were secretly filed against them in March, according to attorneys.

Sudan ranked No. 6 on Open Doors’ 2015 World Watch List of 50 countries where Christians face the most persecution, moving up from the No. 11 spot in 2014.

Last year, the case of Meriam Ibrahim, a Christian woman imprisoned in Khartoum with her child while pregnant, garnered international attention from media and advocacy groups. Ibrahim was sentenced to death for apostasy for converting from Islam to Christianity, but as a result of much international pressure on her case, she was released and permitted to travel to the U.S.

Sudan’s NISS intelligence forces are led by hard-line Islamists who beat, intimidate and arrest the country’s Christians.

The pastors’ families have been waiting with no information about their incarceration or trial.

“We are still worried about their detention,” Ruot’s wife told a Christian advocacy group. “Let us continue to pray for them so that God can help them to be released.”

Marginalization of Christians has dramatically increased since the secession of South Sudan in July 2011.

Sudanese President Omar al-Bashir, a hard-liner, vowed to make Sudan a fully Islamic state operating under the strictest interpretation of Sharia Law, acknowledging only the Muslim religion and the Arabic language.  

The Sudanese Minister of Guidance and Endowments made a declaration in April 2013 that no new licenses would be approved for building or establishing new churches in Sudan.

NISS officials have demanded $12,000 from the Church for the release of the pastors, according to sources close to the case.

Local church leaders said they are fearful to pay this amount, prompting the NISS to arrest other Christians in order to make the same monetary demands.

“Things are getting more and more difficult in Sudan for Christians,” Curry said.

“This case in particular, we feel the charges are trumped up. These are just good citizens practicing their Christian faith, but the Sudanese government is using any tactic they can to push Christianity out of the market place and out of daily life, and unfortunately they are having some success,” according to Curry.

As of 2012, Sudan has deported Christians from foreign countries and demolished church buildings to show Christians they will not tolerate the practice or spread of Christianity within the country.

Due to its treatment of Christians and other human rights violations, Sudan has been designated a ‘Country of Particular Concern’ by the U.S. State Department as of 1999, and the U.S. Commission on International Religious Freedom has recommended the country remain on the list in its 2015 report.

Last year, the Sudanese government destroyed several Christian churches in the capital of Khartoum and in Omdurman and has not allowed any new ones to be built.

Lisa Daftari is a Fox News contributor specializing in Middle Eastern affairs.