Russia planned on selling 2 surface-to-air rocket units armed with P-800, or Yakhont, missiles to Damascus in a deal worth $300 million, Russian media previously reported.
"The contract is on its way to being realized," Interfax news agency quoted Serdyukov as telling reporters in Russia's Far East city of Vladivostok.
Israel has voiced concerns that the sale of the rockets, capable of hitting ships 300 km off Syria's coast, could end up in the hands of Hezbollah.
Hezbollah used a surface to air missile in the 2006 Israel-Lebanon War to hit the INS Hanit warship, killing 4 sailors.
Russia maintains a naval base in Syria.