Russian President Vladimir Putin and his Turkish counterpart, Recep Tayyip Erdogan, on July 6 discussed by phone the supply of Russian S-400 missile defense systems to Turkey as the deal is in the process of being implemented, the Kremlin said.
Asked whether Putin and Erdogan had discussed the delivery, Kremlin spokesman Dmitry Peskov said, "They did mention it, certainly. This is a transaction in the implementation phase."
Ankara's deal with Moscow has been a major source of tension between Turkey and Washington.
The United States has said that if fellow NATO member Turkey does not cancel the S-400 deal by July 31, Ankara will be blocked from purchasing the next-generation F-35 fighter.
Washington has urged Turkey to purchase the U.S.-made Patriot missile system instead.
U.S. President Donald Trump met with Erdogan on the sidelines of last month's G20 summit in Osaka, urging him not to proceed with the purchase of Russia's advanced S-400 ground-to-air defense system.