The deployment of Russia’s advanced S-400 missile defense system in Syria is keeping U.S. jets grounded, given that the sophisticated weapons system can also target aircraft if it needs to, according to the Pentagon. In the aftermath of the downing of a Russian Su-24M jet last month, for which Turkey claimed responsibility, Moscow deployed the system to prevent similar actions from happening again.

"We believe that the measures taken by Russia after the criminal actions of Turkish aircraft, which downed a Russian aircraft — namely the deployment of air defense systems on land and in the sea — is an important step that will ensure more security for Russian and Syrian militaries," Syrian Deputy Foreign Minister Faisal Mekdad said Friday, according to a report by Sputnik, a Russian news website.

While Russia and its Syrian allies claim that the deployment of the S-400 is purely for protection, it has inadvertently grounded U.S. jets, with Pentagon officials claiming that Russia was randomly targeting its aircraft. Since then, the U.S. has flown only unmanned aircraft in Syria, according to a Bloomberg report.

"The increasing number of Russian-supplied advanced air defense systems in Syria … is another example that Russia and the regime seek to complicate the global counter-Daesh coalition’s air campaign," Maj. Tim Smith told Bloomberg Thursday, using an alternative name for the Islamic State terrorist group. "Unlawful actions by Russia and the Syrian regime will not stop coalition counter-Daesh operations in Syria, nor will such actions push the coalition away from specific regions in Syria where Daesh is operating.”

However, Moscow has openly spoken of how it would like to collaborate with the U.S.-led coalition in Syria, in spite of purported military actions against the U.S. military.

“Today, we, again, are faced with a destructive, barbaric ideology, and have no right to allow the new-sprung bigots to reach their goals," Putin said during his annual state of the nation address this month. “We must throw away all quarrels and differences, form a firm first, a unified anti-terrorist front, which will act based on international law and be sponsored by the U.N."