The deal was inked in Erbil, the KRG’s administrative capital, by Elissa Slotkin, U.S. acting assistant secretary of defense for international security affairs, and KRG Interior Minister Karim Sinjari.

The signing was also attended by KRG President Masoud Barzani.

"The main objective of the meeting [which preceded the signing] was to boost cooperation between the KRG and U.S.-led coalition forces," KRG spokesman Umit Sabah told reporters after the signing.

Noting that the protocol was the product of two years of discussions between the KRG and U.S.-led coalition forces, Sabah said that Barzani had met U.S. Defense Secretary Ashton Carter last December with a view to ironing out the agreement’s details.

"The protocol outlines the military roles to be played by the various parties that have lined up against ISIL, with an emphasis on the upcoming liberation of Mosul," Sabah said.