Akar and Mattis exhanged views on defense, the situation in Syria and the fight against terrorism, the source, who spoke on condition of anonymity due to restrictions on talking to the media, said.
Foreign Minister Mevlüt Çavuşoğlu and his American counterpart Mike Pompeo also spoke over the phone Tuesday, discussing relations and the solutions to the existing problems between the two countries.
A delegation led by Deputy Foreign Minister Sedat Önal is set to leave for the U.S. for talks.
Önal and the delegation are expected to discuss the recent escalation between the two countries.
Turkey and the U.S. are currently experiencing rocky relations following the U.S. imposing sanctions on Interior Minister Süleyman Soylu and Justice Minister Abdulhamit Gül for not releasing American Pastor Andrew Craig Brunson, who faces terrorism charges in Turkey.