Some 78 members of the United States Congress urged President Recep Tayyip Erdogan to "immediately" release and deport Rev Andrew Brunson, who has been held since last October.
In a letter they 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."
The politicians said "high-level efforts" had failed to secure of the release of Rev Brunson, who had been working in Turkey since 1993.
Rev Brunson, who pastors the Resurrection Church in Izmir, was arrested on 7th October and told he would be deported as a "threat to national security".
A court jailed Rev Brunson on 9th December 2016 on the grounds of information from a "secret informant" that he had links to a terrorist organisation.
The letter from US politicians continues: "The United States and Turkey have benefited from a close partnership for decades, and we hope to be in a position to continue strengthening these ties.
"In this spirit of partnership, 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.
"We appeal to you to inquire as to the options for promptly deporting Mr Brunson and to act on them expeditiously."
Commenting on the case last year the Christian organisation World Watch Monitor said: "The Interior Ministry has issued similar summary deportation orders against expatriate Christians living in Turkey over the past few years."