Two unnamed senior administration officials and a third person briefed told NBC that the USA and Turkey reached a deal to secure Mr. Brunson's return home.
"We continue to believe Pastor Brunson is innocent, and the hearing on Friday is another opportunity for the Turkish judicial system to free an American citizen", the outlet quoted another unnamed senior administration official as saying.
In addition to the US State Department, Vice President Mike Pence, speaking at a briefing, declined to confirm any deal between Turkey and US, but he voiced hope for Brunson's release.
In July, Turkey moved Brunson from prison to house arrest because of health issues.
Two senior administration officials said there was no deal with Turkey for Brunson. The indictment against Brunson also charges him with having contact with Kurdish separatists that Turkey and the United States have designated as terrorists.
While Brunson's lawyer, Haravut, said he was optimistic about Friday's hearing, he told Yahoo News he was not aware of any deal securing Brunson's release.
The source cautioned that U.S. officials are counting on Turkish officials to follow through on their end of the agreement, which appears to now be in place with Brunson due to appear before a Turkish court on Friday.
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Brunson faces up to 35 years in jail if convicted.
An armored police vehicle is seen outside the home of US pastor Andrew Brunson in Izmir, Turkey October 11, 2018.
"I'm very hopeful that before too long Pastor Brunson ... and his wife will be able to return to the United States", Secretary of State Mike Pompeo said Wednesday.
Officials remained cautious, however, in light of a deal that fell apart last summer, with both sides blaming each other for acting in bad faith.
In August, a Turkish court rejected an appeal for Brunson's release, leading to economic sanctions imposed by President Donald Trump and souring relations between the two North Atlantic Treaty Organisation allies.
"We remain hopeful that with the court proceeding tomorrow that Turkey will see its way clear and free this good man who is guilty of nothing and who has been incarcerated for several years in Turkey unjustly", Pence said.
Mr Brunson is a long-term resident in Turkey. "The current economic challenges have been exaggerated more than necessary and Turkey will overcome these challenges with its own resources", the President declared.
"The Khashoggi affair adds a new variable to a complex question the USA and Turkey had already found quite hard to solve". He has denied the accusation - as has Gulen - and Washington has demanded his immediate release.