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.