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Washington CNN  — 

Amid diplomatic tensions between the US and Turkey on a range of issues, the US State Department announced Tuesday that it approved the possible sale of a $3.5 billion Patriot missile system to Turkey.

The approval is an attempt by the US to get Turkey to give up its plans to purchase the Russian-made S-400 missile defense system. The proposed purchase has been a major impediment to closer US-Turkish relations amid fears the Russian system could allow Moscow to collect intelligence on American and NATO systems.

Turkey’s pursuit of the S-400 has jeopardized its acquisition of the F-35 joint strike fighter, as members of Congress have attempted to block Ankara’s receipt of the jet over concerns about the Russian system.

Kremlin spokesperson Dmitry Peskov said Wednesday that Moscow is moving ahead with agreements to sell the Russian-made S-400 missile-defense system to Turkey, calling the news of the US Patriot missile sale approval “unrelated.”

‘Nothing more, nothing less’

While the announcement came shortly after President Donald Trump spoke to his Turkish counterpart, President Recep Tayyip Erdogan, on Friday, a State Department official denied any connection between the announcement and recent developments, including Trump’s announcement Wednesday that he has decided to pull US troops out of Syria.

“This notification provides a NATO-interoperable alternative to the S-400: nothing more, nothing less. It has no connection to other policy matters,” a State Department spokesman told CNN.

In addition to concerns over Turkey’s purchase of the Russian weapons system, Washington and Ankara have engaged in very public disputes on a wide range of issues, including US support for Kurdish militias in Syria and Washington’s reluctance to extradite exiled cleric Fethullah Gulen, whom Turkey accuses of a coup attempt.

CNN’s Nathan Hodge contributed to this report.