President Recep Tayyip Erdoğan met with U.S. senators on Friday in Istanbul to discuss bilateral relations and cooperation against Daesh and PKK terror organizations.The U.S. delegation was headed by Democratic Party Senator Kirsten Gillibrand. John Bass, U.S. ambassador to Turkey, also attended the meeting.Recent regional developments in Syria and Iraq were also discussed in the meeting. Senators expressed their gratitude to Erdoğan for Turkey's efforts in hosting Syrian refugees and humanitarian aid.The meeting was held in the Mabeyn Mansion of the historic Yıldız Palace complex and lasted around two hours.Prime Minister Ahmet Davutoğlu also met with the delegation in Prime Ministerial Office in Dolmabahçe Palace on late Friday.