Weapons delivered to the PKK/PYD terrorist group will be taken back after Daesh is defeated, U.S. Defense Secretary Jim Mattis said in a letter sent to his Turkish counterpart on Thursday.

According to a Turkish National Defense Ministry source, James Mattis told Fikri Isik that the U.S. had taken intensive and determined measures regarding Turkey's security concerns, and would provide a monthly list of the weapons and equipment supplied to the group, recalling that the first inventory list was submitted earlier in June.

The PKK/PYD is the Syrian offshoot of the PKK, designated a terrorist organization by Turkey, the U.S. and EU. However, the U.S. views the PKK/PYD as its ground ally against Daesh and has armed the group despite the protests of its NATO ally Turkey.