ISTANBUL (Reuters) - The replacement of the main prosecutor in the trial of an American pastor in Turkey may be a positive change, the lawyer for the clergyman told Reuters on Thursday, though he said it would be wrong to expect it to herald his release.

FILE PHOTO: U.S. pastor Andrew Brunson reacts as he arrives at his home after being released from the prison in Izmir, Turkey July 25, 2018. Demiroren News Agency/DHA via REUTERS/File Photo

The case of Andrew Brunson, an evangelical pastor, who has lived in Turkey for decades and is being tried on terrorism charges, has been at the center of a bitter row between NATO allies Washington and Ankara.

The crisis has prompted President Donald Trump to impose sanctions on Turkey and double trade tariffs, exacerbating a slide in Turkey’s lira which reverberated across global markets.

After being detained for 21 months, Brunson was moved to house arrest in July with a travel ban. If found guilty, he could be jailed for up to 35 years. He denies the charges.

On Wednesday, the main prosecutor who has prepared the case against Brunson was removed from the case. No explanation was provided, although changes of judges or prosecutors mid-case are not uncommon in Turkey.

“The prosecutor has had a negative impact on the direction of the trial,” Ismail Cem Halavurt, Brunson’s lawyer said. “He has constantly added fresh testimonies from anonymous witnesses who had nothing to do with my client,” he said.

“Now his removal might be a sign that the will about this case is changing,” he said, but added: “It is not right to say that he might be freed based on this development. We will have to wait and see.”

While Turkish prosecutors are frequently replaced half way through a trial, the move has attracted attention given the high stakes in the case.

Washington has turned the Brunson affair, one of several disputes it has with Turkey, into the central issue to be resolved as a condition to improve relations.

President Tayyip Erdogan linked the cleric’s release to Turkey’s demand for Washington to extradite Fethullah Gulen, a Pennsylvania-based imam and former AKP ally who Turkey says was behind the abortive putsch of July 2016. He denies the accusation.

Trump last month demanded the unconditional release of Brunson, calling him a “great patriot hostage”, after the collapse of a deal that might have freed him.

Ankara has repeatedly said the case must be decided by the courts, slamming what it said was the United States’ disregard for Turkey’s legal process. Brunson’s next hearing is scheduled for Oct. 12.