"Everything is on track with the Turks. I hope that we will begin to deliver in about two months," Sergei Chemezov told NTV channel, according to Russian agencies.

"The credit money has been spent, the technology was produced. And we completed training of all the military personnel," he said.

Turkey's S-400 purchase has ruffled feathers in the US, and Pentagon officials warned of "devastating consequences" for the NATO member which also plans to buy F-35 fighters from the US.

Washington wanted Turkey to opt for American Patriot missiles instead of the S-400 system, but President Recep Tayyip Erdogan said that Russia made a better proposal.

He said this week Turkey was "determined" to buy from Russia.

Russian agencies reported that the purchase concerns four systems valued at $2.5 billion.