ANKARA, Turkey (AP) — Turkish President Recep Tayyip Erdogan says Russia's S-400 air defense missiles are currently being prepared to be flown to Turkey.

Speaking to reporters before leaving for Bosnia on Monday, Erdogan wouldn't say, however, when the Russian missile defense system would reach Turkey or where they will be deployed.

The delivery of the systems could bring Turkey closer to U.S. sanctions. U.S. officials have warned that Turkey would face economic sanctions as well as being expelled from a program to produce the F-35 fighter jets.

Turkey has refused to pull back from the deal.

Erdogan said: "The preparations for the journey, the loading (of the S-400) is continuing ... The S-400 will arrive by planes. May it be beneficial for our country, our region and especially for the world."