The Israel Air Force is deliberating whether to buy an improved model of the US-made Patriot missile defense system. Lockheed Martin offered the system, know as the PAC-3, to the IDF for the relatively low price of under $50 million, defense industry sources said. Israel's missile defense systems consist of the Arrow, which is designed to intercept long-range ballistic missiles like the Iranian Shihab, and the PAC-2, also known as the Patriot, which is used as a second level of defense if the Arrow fails. The PAC-3 is one of the only operational missile defense systems deployed around the world. The US Army received its 500th missile from Lockheed Martin on Sunday. The PAC-3 is believed to be capable of intercepting most of Syria's missiles. It is an improved version of the PAC-2 in terms of coverage and lethality. The PAC-3 has an interceptor missile that uses a hit-to-kill system rather than an exploding warhead used by the PAC-2. The PAC-3 missile is also smaller and its launchers can fire 16 instead of just four like the PAC-2. The Defense Ministry's Homa Missile Defense Agency has expressed interest in purchasing the PAC-3. In April, Homa director Arieh Herzog told The Jerusalem Post the system would assist Israel in maintaining a defensive shield against enemy missiles. The decision to buy the PAC-3 will be made over the coming week. Chief of General Staff Lt.-Gen. Gabi Ashkenazi will convene his top generals for a week-long workshop to determine the IDF's procurement plan for the coming years. According to the proposal presented to the IAF, Israel would not need to buy complete and new platforms. It would just need to modify and upgrade the PAC-3's missile launchers and radar system to accommodate the PAC-3. Meanwhile, Syria began receiving the first shipment of Russian-made antiaircraft missile and gun-range, land-based Pantsyr-S1 defense systems (SA-22 E in NATO terminology) on Sunday. The missile system has a range of 12 kilometers and threatens IDF aircraft over the Golan Heights. The antiaircraft missiles are part of a $900 million deal that Russia signed with Damascus at the beginning of the year for 50 Pantsyr-S1 batteries and missiles. The procurement of the missiles poses a tactical challenge for the IAF and puts into question its training regimen, which includes flying aircraft during exercises in the Golan Heights. While Israel has voiced strong objections to Russian arms deals with Syria and Iran, Moscow has said it will continue supplying Middle Eastern countries with military platforms of a defensive nature. The system carries 12 surface-to-air missiles on launchers arranged in two six-tube groups. The missile weighs 65 kilograms, carries a warhead that weighs 16 kg and is capable of downing an IAF fighter or reconnaissance jet.