US President Donald Trump on Monday signed a defense bill that contains a provision suspending the delivery of F-35 Joint Strike Fighters to Turkey.

Turkey and the US remain in a standoff over the fate of Andrew Brunson, a pastor detained in Turkey who is accused of spying. Trump has called on Turkey to return Brunson to the US and has said the cleric is being persecuted for “no reason.”

In July, Brunson was moved to house arrest from pretrial detention, where he has been since October 2016.

Ankara was seeking to take delivery of at least 100 of the stealth jets. However, various legislators have cited a number of concerns with Turkey, including its plans to buy an advanced Russian air defense system, warming ties with Moscow and the arrest of US citizens and consulate staff, including Brunson.

Turkish Foreign Minister Mevlüt Çavuşoğlu on June 4 emphasized that if Washington decides not to deliver the F-35s to Turkey, Ankara will look to other countries or produce its own.