Top U.S. military official Joseph Dunford hopes Washington would find a way to resolve a dispute with Turkey.

He commented on Turkey’s decision to purchase Russia’s S-400 air defense system as well as on the reports that U.S. might suspend the supplies of F 35 fighter jets to Ankara, Reuters reported.

General Joseph Dunford, the chairman of the U.S. Joint Chiefs of Staff, said: “Both the executive branch of our government and legislative branch of our government are going to have a hard time reconciling the presence of the S-400 and the most advanced fighter aircraft that we have, the F-35.”

Turkey is manufacturing elements for F-35 fighter jets. Earlier Ankara said they are going to but up to 100 jets, and the first two were handed over to Turkey in June 2018. It was supposed that two F-35 jets would be sent to Turkey as soon as the pilots complete their trainings, that is in November 2019.

Despite U.S. discontent and warnings about possible sanctions, Turkey said they would not reject S-400 deal with Russia.