Supporters of a US pastor who has been jailed on charges of 'membership in an armed terrorist organisation' since October say their legal defence is struggling.
Rev Andrew Brunson of North Carolina has been held in Turkey since October. Brunson, 71, led a Protestant church in Izmir, Turkey, but was accused of connections to the US-based cleric Fetullah Gulen, who Turkey alleges was involved in a coup attempt last summer.
The legal case for Brunson has been struggling due to lack of information provided by the Turkish authorities, Fox News reports.
'The problem we have is that his file is sealed, his Turkish attorney doesn't have access to the file, and there hasn't been any evidence that has been presented,' said Cece Heil of the American Center for Law & Justice (ACLJ), a non-profit law firm supporting Brunson's case.
'It's been extremely hard to prepare any defence or to know what is at issue here,' she said, adding 'we have no idea why' Brunson was detained.
'He was a pastor in Turkey for 23 years with no problem.'
Last week US Republicans and Democrats in Congress made a bi-partisan appeal to the Turkish government led by President Recep Tayyip Erdogan. Their joint letter demanded the pastor's immediate release and deportation.
'Mr. Brunson has worked peacefully in Turkey since 1993,' the address to Erdogan said. 'There appears to be no evidence to substantiate the charges against him for membership in an armed terrorist organization. Moreover, your government has repeatedly denied regular and appropriate access to legal counsel and American consular services.
'We respectfully ask you to consider Mr Brunson's case and how the recent treatment of Mr Brunson places significant strain not only on him and his family, but also on the robust bilateral relationship between the United States and Turkey.'
The letter also called for the country to 'reaffirm respect for fundamental freedoms and the rule of law'. The ACLJ also sent a letter to secretary of state Rex Tillerson urging his support.
President Erdogan's rule has been increasingly authoritarian since a failed coup last year, with tens of thousands of people arrested or dismissed from their jobs. A referendum in April is set to give him sweeping powers and entrench his political position for years.