Syria's president says the country has received the first shipment of an advanced Russian air defence system.
President Bashar al-Assad is also reported to have told the Hezbollah-linked Al Manar television station that the tide of the war was turning in the government's favour.
Russia vowed this week to go ahead with sending the weapons soon after an European Union decision to life an arms embargo on Syria, the BBC reports.
The delivery of such missiles on Thursday raises fears of further tension with Israel, as Syria has said it would respond directly if Israel launched any further air attacks on its territory.
"Syria has received the first shipment of Russian anti-aircraft S-300 rockets," Al Manar quoted Mr Assad as saying in an interview due to be broadcast on Thursday. "The rest of the shipment will arrive soon."
The S-300 is a highly capable surface-to-air missile system that, as well as targeting aircraft, also has the capacity to engage ballistic missiles.
Meanwhile, the United States has demanded that Hezbollah withdraw its fighters immediately, saying their presence in Syria is unacceptable and dangerous.
The comments came after the United Nations Human Rights Council condemned the involvement of foreign fighters in the city of Qusair.
Washington has no leverage over Hezbollah and the warning did not come with any threat of consequences if the Lebanses militant group doesn't leave.
But the statement is a sign of growing concern in the US that the two-year conflict is morphing into complex regional war by proxy.
A State Department spokesperson said that Hezbollah's active role in combat in Syria is an uncceptable and extremely dangerous escalation.
The Syrian rebels' military commander General Salim Idriss has appealed to Western powers, saying: "We are dying, please come and help us."