Russia will deliver an anti-aircraft missile system to Serbia even though the U.S. has warned of possible sanctions against the Balkan country in case of such purchases.

Russia's state TASS news agency said Wednesday that the Pantsir-S system will be delivered to Serbia "in the next few months in accordance with the signed contract."

The U.S.'s special envoy for the Western Balkans, Matthew Palmer, warned Serbia last week that the purchase of Russian weapons "poses a risk" of U.S. sanctions.

Last month, Moscow sent a S-400 missile system battalion and a Pantsir to Belgrade for their first joint drills in Serbia.

Serbia remains a key ally of Russia even though it wants to join the European Union.

Belgrade has pledged to stay out of NATO and refused to join Western sanctions against Russia over the conflict in eastern Ukraine.

Pantsir is a truck-mounted short to medium range surface-to-air missile and anti-aircraft artillery weapons system possessed by Russia and regime of Bashar Assad in Syria. Known to be deployed by Russia at or near its Hemeimeem air base and at its Tartus naval facility. It has been fired in Syria a number of times to take out drones and missiles. The system can shoot down cruise missiles.