The U.S. is still holding talks with Turkey insisting that Ankara should ‘walk away’ from S400 Russian missile defense system that it purchased, a U.S. official said.

Washington is pressing Turkey to either send it back or not make it operational, the Voice of America reported.

The discussion is a part of dialogue with Ankara aimed at solving the problems in US-Turkey relations. According to the source, Washington is still ready to impose sanctions within under a law known as Countering America's Adversaries Through Sanctions Act (CATSAA) over Turkey’s purchase of S400.