Defense Secretary Ashton Carter says he doesn't believe Russia's claims that its violation of Turkish airspace over the weekend was an accident and is promising to respond.
"I do not believe that it is accidental," he said during a press briefing at Morón Air Base in Seville, Spain on Tuesday, where he visited troops. "We will react to that, and certainly the Turks will and have said they will. So it's a serious matter. We take it very, very seriously."
NATO said on Monday that Russian fighter aircraft violated Turkish airspace on Saturday and Sunday. Turkey said in Saturday's incursion, two Turkish F-16 fighter jets intercepted the aircraft and the Russian planes departed.
Carter said he would discuss the matter with NATO on Thursday. The incident threatens to escalate an already tense relationship between the U.S. and Russia.
The two world powers are currently on opposing sides in Syria, where U.S. and coalition forces are striking Islamic State in Iraq and Syria (ISIS) targets, and supporting rebel groups that are fighting ISIS.
Despite U.S. warnings, Russia began its air campaign last week in Syria to target "terrorists." But U.S. officials say they have hit the same anti-regime rebel groups backed by the U.S. in a bid to boost ally Syrian President Bashar al-Assad.
The U.S. is reportedly working with Turkey and other members of an anti-ISIS coalition to open an offensive in northern Syria, to shore up Kurds and rebel groups, and increase airstrikes against ISIS from a base in southern Turkey.
Pentagon officials began a first round of talks with Russian counterparts last week to discuss avoiding conflicts in the airspace over Syria and professional airspace conduct, but Carter said the Russians “have yet to respond to us."
“We are waiting for the Russians. They owe us a response,” he said. “They should come in and do it right now.”
He said the Russians wanted the talks in the first place, and their lack of follow-up “may be a further sign of their strategic confusion.”
Carter said Russia's military campaign in Syria "a very wrongheaded and backward approach that's sure to backfire,” and that reports it will send in “volunteer” ground troops would only deepen their mistake.
"It's just going to fuel the Syrian civil war. And so, is a serious strategic mistake on the part of the Russians," he said.
However, Carter did not say what the U.S. would do about Russia's moves in Syria, and said the U.S. would continue its own operations with allies there.
"Reality is going to be the first check on the Russians," he said. "We'll continue to tell the Russians they have to conduct themselves professionally, but they're making a serious strategic mistake," he said.