Turkish President Recep Tayyip Erdogan stated publicly that his country would shutdown two strategic military bases in the country, currently used by the United States, if Washington decides to implement sanctions for Ankara’s decision to purchase S-400 missile systems from Russia.

Erdogan specified that “if necessary, we’ll close Incirlik and also Kurecik,” and that if sanctions are enacted by the U.S., “we’ll respond to them in the framework of reciprocity.”

This was not the first time that Turkish officials have raised the prospect of closing down the bases as a form of retaliation. A few days earlier, Turkish Foreign Minister Mevlut Cavusoglu also discussed the possibility.

Most notable of the two bases is Incirlik from where the U.S. Air Force operated during its campaign against ISIS in both Iraq and Syria. The base has also seen use for wider operations in the region. In addition, it currently houses an estimated 50 B-61 gravity nuclear bombs.

Kurecik, located in the east of the country, currently also serves as a NATO radar base.

It remains to be seen whether or not Turkey will actually carry out its threat. Recent posturing by Erdogan, however, would suggest that it is very much a real possibility. In addition to invading northern Syria, shooting down a Russian fighter jet in 2015, as well as constantly rebuffing U.S. threats such as by personally returning a letter written by President Donald Trump, the Turkish leader has shown that he is not easily deterred.

Erdogan threatens closure of US military bases in Turkey

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Pressure has mounted in the U.S. to impose sanctions on the eastern Mediterranean country for its decision to buy Russian-made missiles. Members of both major parties in Congress have pushed for a tougher policy on Turkey. In response, during the NATO summit earlier this month, Erdogan made it clear that he would oppose a NATO defence plan for the Baltic states and Poland if the transatlantic alliance refused to classify the Syrian Kurdish YPG as a terrorist organization.

Earlier this year, the U.S. removed Turkey from its F-35 program.

Should Turkey close down the bases and force the U.S. and NATO forces to leave, it would significantly reduce any remaining leverage it has. On the other hand, continued U.S. antagonism towards Turkey could push it further into the arms of Russia, with which it’s already discussing further cooperation.

Growing friction with Turkey is not limited to just the field of military affairs. Erdogan also threatened to respond to the decision of the U.S. Congress to recognize the Armenian genocide. While Trump has not yet signed the resolution — and previous administrations have also been wary of the issue — the current milieu might make it more likely that he will, especially in light of his erratic and unpredictable attitude towards foreign leaders.

The expulsion of NATO forces would offer Turkey considerable influence in larger decision-making. The country’s strategic geographic position makes it a crucial partner. However, the quarrel could result in the U.S. and its partners increasingly relying on their Gulf allies. The U.S. already has a naval base in Qatar and a naval support base in Bahrain, in addition to having sent troops to Saudi Arabia in recent months.