Acting U.S. Defense Secretary Mark Esper will speak by telephone with his Turkish counterpart later Friday following Turkey's receipt of Russian S-400 missile defense system components.
The Trump administration has threatened to expel Turkey and Turkish firms from the advanced F-35 jet fighter over concerns the Russian system could be used by Russia to gain sensitive data on the jet.
The U.S. has also threatened sanctions over the S-400 purchase, with Turkey responding that any sanctions would be met in kind.
Local media quoted Esper as saying the U.S. position on the F-35 has not changed.
The Pentagon is expected to brief reporters later Friday on the matter following Esper's conversation with Akar.
Turkey agreed in April 2017 to purchase the S-400 system from Russia following lengthy efforts to purchase an air defense system from the U.S. with no success.