MOSCOW, July 29 (Xinhua) -- Russia has agreed to deliver S-300 air defense systems to Azerbaijan in a deal worth at least 300 million U.S. dollars, Russian business daily Vedomosti reported Thursday, citing official sources.

　　Russian state arms exporter Rosoboronexport signed an agreement with the Azerbaijani Defense Ministry for the supply of two S-300 PMU-2 (Favorit) battalions last year.

　　The deal is believed to be the most expensive single purchase of heavy weaponry by a former Soviet State.

　　Belarus, Kazakhstan and Algeria have previously purchased the S-300 systems. In 2005, Russia also signed a contract to sell at least five S-300 missiles to Iran.

　　Russian Defense Ministry said the latest deal would unlikely change the balance in power between Azerbaijan and another former Soviet republic, Armenia, which have experienced tension and conflicts over the region of Nagorno-Karabakh.

　　The S-300 air defense system is an advanced mobile system that can shoot down aircraft and cruise missiles from up to 150 km away.