Turkish TV showed amateur video purportedly showing the test firing of the Russian anti-aircraft weapon system by the Black Sea. Washington said the test was "incompatible" with the responsibilities as a NATO ally.
The United States on Friday condemned NATO ally Turkey after it reportedly carried out its first test of a highly advanced Russian air defense system in defiance of US warnings.
Amateur video, taken in the Black Sea city of Sinop, showed a narrow column of smoke headed high into the blue sky, which local media said came from the S-400 missile system.
Turkey's defense ministry said it would neither deny nor confirm missile tests in the area, but in recent days, Ankara had issued notices restricting air space and waters off the coastal area to allow firing tests.
Last week, footage emerged on social media showing what appeared to be trucks carrying S-400 batteries to Sinop.
If verified, the test could stoke tensions between Turkey and the United States, which sharply opposed Ankara's purchase of the weapons from Moscow on grounds they compromise shared NATO defense systems.
The US State Department wouldn't confirm the test but warned of "potentially serious consequences" if Ankara activates the weapon, with the threat of sanctions hanging in the background.
"If confirmed, we would condemn in the strongest terms the S-400 test missile launch as incompatible with Turkey's responsibilities as a NATO Ally and strategic partner of the United States," State Department spokesperson Morgan Ortagus said in an email.
"The United States has been clear on our expectation that the S-400 system should not be operationalized," she said.
Russia has regularly shown off its S-400 missile defense system, including at this Victory Day parade in Moscow
Turkey signed the S-400 deal with Moscow in 2017 and deliveries of the first four missile batteries, worth $2.5 billion, began in July last year.
One of the best air defense systems of its kind, the S-400 has the potential to engage airborne targets about 400 kilometers away.
Washington reacted by suspending Turkey from its F-35 jet joint manufacturing program and has threatened sanctions.
Ankara defended its position by saying that the United States refused to sell it the competing American Patriots, an assertion disputed by former US officials, but which US President Donald Trump has agreed with.
Turkey has been a member of NATO since 1952 but has seen rising friction with the West on multiple fronts, including the war in Syria and the renewed conflict in the disputed South Caucasus region of Nagorno-Karabakh.
This week, the US, France and Germany also sharply criticized Ankara for sending an energy exploration vessel back to hunt in waters disputed with fellow NATO ally Greece.
mm/rc (AFP, AP, Reuters)