Defense Secretary Ash Carter will meet with his Turkish counterpart this week in the midst of a four-day trip to the U.K. and Norway, the Pentagon announced.

Carter’s meeting with Turkey’s Minister of National Defense Fikri Isik comes during a sensitive time, as the U.S. relies on the NATO ally’s air base in the fight against the Islamic State in Iraq and Syria, yet has also partnered with the Kurdish YPG group, which Ankara considers a terrorist organization.