A Turkish court sentenced U.S. consulate employee Metin Topuz to eight years and nine months in jail for aiding a terrorist organisation, state-owned Anadolu news agency said on Thursday, a development that could strain ties with Washington.

Topuz’s trial has been one of several sources of friction between NATO allies Turkey and the United States, who have also been at odds in recent years over policy differences in Syria and Turkey’s purchase of Russian missile defence systems.