Recep Tayyip Erdogan
Recep Tayyip ErdoganReuters

Turkey's deal to buy Russian S-400 missile defense systems had "nothing to do" with the security of the US, President Recep Tayyip Erdogan said Saturday, according to AFP.

He was speaking a day after Washington warned Ankara of "grave consequences" should the deal go ahead.

"It is very clear why Turkey has bought this air defense system, under what conditions it has bought them and how it will be used," Erdogan said in the southeastern city of Diyarbakir.

"Everyone knows that this issue has nothing to do whatsoever with NATO, the F-35 project and the security of the US," he added.

The "issue was not about the S-400s" but about Turkey "taking actions on its own accord", especially in Syria, continued Erdogan.

Ankara's push to buy the systems from Moscow has caused tensions with the US, its NATO ally.

Military experts are concerned that the deployment of S-400s would put the security of allied weapon systems, particularly F-35 aircraft and radar facilities, in danger.

The US believes the S-400 sale is part of Russian efforts to disrupt the alliance amid Western concern over Erdogan's burgeoning relationship with Russian President Vladimir Putin.

US Defense Department spokesman Charlie Summers said on Friday there would be "grave consequences" for Turkey if it went ahead with the deal.

Turkey would withhold F-35 fighter jets or US Patriot missiles approved for sale to Ankara in December for $3.5 billion, he warned.

Earlier this week, a top US general said he would recommend that the United States withhold delivery of F-35 fighter jets to Turkey if Ankara goes through with the purchase of the Russian S-400 air defense system.

The United States recently approved the sale of $3.5 billion in missiles to Turkey in a move seen as a counter move to Turkey’s purchase of the S-400 from Russia.

In January, Turkey rejected a US offer to cancel its purchase of S-400 missiles from Russia. This came after a spokesman for Erdogan made clear that Turkey’s purchase of US missiles will not affect its deal to acquire rival S-400 missiles from Russia.