Turkey is to conduct a test of the Russian S-400 missile defence system next week, angering the US and causing it to be "deeply concerned".
According to the US news site Bloomberg, which cited sources familiar with the matter, Turkey will be conducting the comprehensive test of the defence system it purchased from Russia, primarily to observe the readiness of Turkish military personnel at the test site in the northern Sinop province on the coast of the Black Sea. These tests will reportedly not involve activating the system's batteries.
Turkey's purchase of the Russian-made missile defence system has been a cause of tensions between the country and the US over the past two years, with Washington constantly urging Ankara to return the system to Moscow. It also made it a condition for selling its own Patriot missile system to Turkey, but President Recep Tayyip Erdogan has previously refused to give up the S-400 system.
Turkey's decision has also been a point of controversy in the NATO alliance with many claiming that the S-400 system would compromise the group's own security apparatus and enable its rival Russia to gain access to the alliance's military capabilities.
The report of Turkey's planned test came shortly after previous reports yesterday that its military had been spotted moving components of the S-400 system to the Black Sea city of Samsun.
Following these reports, the US expressed its deep concerns over the planned test, with a State Department spokesperson telling the Russian news site Sputnik: "We are aware of these reports. We continue to object strenuously to Turkey's purchase of the S-400 air defense system, and are deeply concerned with reports that Turkey is continuing its efforts to bring the S-400 into operation."
The spokesperson also referenced the US' suspension of Turkey from the joint F-35 fighter jet programme last year, stating that it "signalled the seriousness with which the Administration approaches this issue." The State Department concluded stressing "at the highest levels that the S-400 transaction remains a major obstacle in the bilateral relationship and at NATO, as well as a risk for potential CAATSA sanctions. We are confident that President Erdogan and his senior officials understand our position."
The administration of US President Donald Trump has so far not sanctioned Turkey over the S-400 issue despite increasing calls from Congress to do so. If the government did decide to diplomatically retaliate against Turkey, it could enact sanctions through the Countering America's Adversaries Through Sanctions Act (CAATSA), as it has already done for countries such as Iran, North Korea and Russia itself.
Although sanctions have not been imposed on Turkey, it was revealed two months ago that US Congress was secretly blocking major arms deals to Turkey for the past two years over the S-400 issue.