ANKARA, Aug. 7 (Xinhua) -- Turkish Defense Minister Hulusi Akar and his U.S. counterpart James Mattis had a phone conversation on Tuesday amid political crisis over detention of U.S. pastor Andrew Brunson in Turkey.

The two ministers discussed defense relations, Syria and fighting against terrorism, state-run Anadolu Agency reported.

The phone conversation comes amid diplomatic spat after the U.S. Department of the Treasury imposed sanctions against two Turkish ministers on the ground that they have "played leading roles in the organizations which were responsible for the arrest and detention of pastor Brunson."

Andrew Brunson, a 50-year-old Christian pastor, was detained two years ago in Turkey on spying charges, and faces up to 35 years in prison if found guilty.

Turkey and the U.S. have been cooperating on a road map for withdrawal of Syrian Kurds from northwestern Manbij town of Syria.

Ties between the two NATO countries were already strained as the U.S. Congress threatens to block the sale of F-35 fighter jets to Turkey over the continued detention of pastor Brunson and the purchase of S-400 missiles from Russia.