Russian naval ships during an military exercise. Photo: Wikipedia.

Three Russian warships spotted in the eastern Mediterranean are believed to be carrying weapons shipments that might be used to resupply the Syrian regime, a Pentagon official told CNN Wednesday night.

According to the report, the United States has been tracking the ships since they left a Russian port several days ago. Though unconfirmed, it is believed that containers witnessed being loaded onto the ships could contain components of the controversial S-300 missile defense system.

The U.S. and Israel have urged the Russians to halt plans to transfer the system to the Syrian regime for fear that it will strengthen Syria’s already formidable air defense capabilities. But Russia has thus far been noncommittal, with Russian President Vladimir Putin defending his country’s decision Tuesday to go through with the transaction, though he said the S-300 system had not been delivered–yet.