The S-300 anti-aircraft missile system at the Victory Parade, Red Square, 2009. Photo: Wikipedia.

Russia has not yet delivered the promised advanced S-300 missile systems to Syria, but maintains it plans to by next Summer, Russia’s Vedomosti daily reported Friday, citing arms industry sources.

Several of the systems were due to be sent to Syria this Spring, but Russia decided to delay the delivery in an effort not to upset the balance of power in the region, according to the report.

Syria ordered four S-300 systems in 2011 at a cost of $1 billion, two sources in the arms industry told Vedomosti, adding that several of the S-300s have already been built, while the production of the others has been postponed. Syria has paid a deposit of several hundred million dollars, the sources said.

Syrian Deputy Prime Minister Qadri Jamil said in July during a visit to Moscow that all the contracts to deliver arms from Russia to Syria were still in place.

Earlier in the year, Syrian President Bashar al-Assad claimed that Russia has already begun delivering the system, but Russia refuted this claim and the miscommunication was later attributed to a translation error, Vedemosti reported.

Russian plans to deliver the S-300 system to Syria have angered the US and Arab states that oppose Syrian President Bashar al-Assad as they fear that he could gain a decisive tactical edge with the acquisition.