Russia’s shipment of alleged missiles to Syria could “embolden” the regime’s forces and prolong the country’s civil war, a top U.S. military official said on Friday.

If fresh media reports are true, Russia, Syria’s longtime supplier of military equipment, may soon provide Damascus - or already has - with advanced S-300 air defense systems, tipping the balance in the devastating 26-month conflict in the Middle Eastern country. But the “if” is a big one.

Israel warned the United States in recent days that Russia plans to sell advanced ground-to-air missile systems to Syria despite Western pressure on Moscow to hold off on such a move, the Wall Street Journal (WSJ) reported on Wednesday.

The United States and Russia on Tuesday agreed to push both warring sides in the Syria conflict to find a negotiated solution and to hold an international conference in search of peace.