Syria has begun payments to Russia for S-300 anti-aircraft missiles, intended to keep foreign interference out of the 2-year civil conflict.
Israel, which has already conducted three sets of air strikes on Syria so far in 2013, promised to make sure the missiles never arrive.
"The shipments haven't set out yet and I hope they won't," Israeli Defense Minister Moshe Ya'alo said. "If they do arrive in Syria, God forbid, we'll know what to do."
Russia has justified the sale as a stabilizing measure against the potential interference of "some hotheads" into the conflict just as the European Union lifted the ban on selling weapons to Syrian rebel forces.