The United States on Friday condemned Turkey after it reportedly carried out its first test of a highly advanced Russian air defense system in defiance of US warnings.
The Turkish army conducted the test firing of the S400 missile defense system in the northern province of Sinop by the Black Sea, according to the pro-government television station A Haber.
Other Turkish media have shared an amateur video showing a white streak in the sky.
The defense ministry refused to confirm or deny the test firing.
In Washington, the State Department said that it had warned its NATO ally at high levels that the acquisition of the S400s was "unacceptable.”
"If confirmed, we would condemn in the strongest terms the S400 test missile launch as incompatible with Turkey's responsibilities as a NATO ally and strategic partner of the United states," State Department spokeswoman Morgan Ortagus said.
In response to the delivery of the first battery last year, the United States suspended Turkey from the production program of F-35 fighter jets.
Washington also threatened Ankara with sanctions if the S400s were activated -- but had held out hope that Turkey would "keep it in the box."
"The United States has been clear on our expectation that the S400 system should not be operationalized," Ortagus said.
"We have also been clear on the potential serious consequences for our security relationship if Turkey activates the system," she said.
Despite repeated warnings, President Recep Tayyip Erdogan has repeatedly asserted that the S400s will be deployed.