ANKARA, May 31 (Reuters) – The delivery schedule for Russia’s S-400 missile defence systems to Turkey is continuing as planned, Turkish Foreign Ministry Spokesman Hami Aksoy said on Friday, dismissing reports of delay.

The U.S. and Turkey have been at odds over Ankara’s decision to purchase the S-400’s, which Washington says are not compatible with NATO systems and poses a threat to the F-35 stealth fighter jets. Ankara has proposed to form a working group to assess the U.S. concerns, but has not received a response yet.

On Monday, broadcaster Haberturk quoted Turkish Defence Minister Hulusi Akar as saying that the delivery of the S-400’s may not happen in June, when Turkey previously said the missiles were due to arrive, but added the agreement was a done deal.

“Reports in some media outlets about Turkey evaluating delaying the S-400 procurement upon the request of the United States do not reflect the truth,” Aksoy said in a statement, adding that Ankara’s offer for a joint working group with Washington was still valid.

(Reporting by Tuvan Gumrukcu and Ece Toksabay)

U.S. Air Force F-35A