Defense Minister Fikri Işık said on Friday that Ankara and the Kremlin are about to take the last step in the S-400 missile issue, adding that NATO should demonstrate understanding about the situation.

Speaking at a press conference, Işık said the two sides are in final negotiations concerning S-400 missiles. "It is very obvious that Turkey needs an air and missile defense system ... Unfortunately, NATO member states have not produced an offer at an effective cost," Işık said, adding that this has forced Ankara to search for other sources.

Stressing that Ankara knows the S-400 missile system cannot be integrated into the NATO system, Işık said NATO should understand this matter. The minister asserted that NATO does not have the right to tell Turkey to refrain from buying the S-400 system.

The S-400 was developed as an upgraded version of the S-300 series of surface-to-air missile systems.

The system entered service in April 2007, and the first S-400 was deployed in combat in August 2007.

According to sources within the defense industry, a regular S-400 battalion consists of at least eight launchers with 32 missiles and a mobile command post.