Turkey has once again defied US calls to abandon a deal for the purchase of Russian S-400 missile defense systems, repeating an offer for a NATO-led working group to resolve the long-running dispute with Washington.

A senior aide to Turkey’s President Recep Tayyip Erdogan says the country is determined to go on with the purchase of Russian S-400 missile defense systems, despite threats of sanctions by the United States.

Russia has begun delivering the 2nd batch of its advanced S-400 missile defense systems to China as part of a 2014 contract.

India has approved a plan to purchase five Russian-built S-400 Triumph defense systems, despite earlier warnings from the US against any military transaction with Russia.

Turkey has reportedly begun building a site for the advanced Russian-built S-400 air defense missile system, regardless of strong opposition from the United States to the plan and warnings that Ankara should not buy the anti-aircraft platform.