"A contract on deliveries of the Strelets air defense system has not been signed, and it is hard to say when it will be signed," Sergei Chemezov said, adding that the negotiations have been complicated.
"They [the Syrians] want the Igla portable air defense system, but we have refused to supply it," he said.
Syria first has to decide whether it wants to purchase the Strelets system or not, the Russian official said.
Syria, a long-time client of Russia's defense industry, has accounted for up to four percent of Russia's annual arms sales, which totaled a record $6.1 billion last year.
However, it is unclear whether the head of Rosoboronexport was referring to a new contract or to part of the previous agreement, which was signed in April 2005.
The details of the deal have never been made public, but Valery Kashin, head of the Kolomna-based Engineering Design Bureau, which designed the Strelets system, said earlier that Russia met all of its commitments in 2006 under the contract to supply Syria with the Strelets system, confirming the delivery of equipment under the 2005 contract.
Russia agreed in 2005 to sell Syria short-range anti-aircraft missile systems to bolster its capability to protect strategically important facilities from "potential air strikes."
Israel and the United States spoke out against the 2005 deal, claiming that Syria would pass on the system, which fires Igla ground-to-air missiles, to Hezbollah guerrillas in Lebanon.
Russia has consistently defended the deal, saying that "international agreements place no restrictions" on the sale of such missiles.
According to the Russian Defense Ministry, the Strelets is a vehicle-mounted launcher rather than a portable system, such as the Igla-S air defense system, which can be fired from the shoulder at an aircraft or helicopter, a cruise missile or any other aerial target.
Although both use the same method of operation, there is a big difference between the two systems.
Like the U.S. Stinger, the Igla-S is an autonomous portable system, weighing about 15 kilograms (30 pounds) that can be fired by a trained operator at any time of day or night, regardless of the weather, at approaching or receding targets, and regardless of electronic or thermal interference.
In the hands of terrorists, it could represent a formidable threat to any aerial target flying at an altitude of 10 meters (30 feet) to 3.5 kilometers (2 miles), and at a distance of up to 6 kilometers (3.7 miles)
The Strelets, on the contrary, is a heavy-weapon system comprising control and launch elements (modules) that can fire two to eight Igla-S missiles separately or in a salvo. The tactical and technical characteristics of the Strelets and the Igla are the same, but the Strelets must be mounted on a rail-pad placed on a vehicle (like a Jeep), the turret of an armored car, a patrol boat, or on the undercarriage of a helicopter gunship.
A missile can be fired from the Strelets only if it is mounted on a platform - it is impossible to shoulder-fire a missile from a system that weighs anywhere between 80 kilograms (180 pounds) and 120 kilograms (400 pounds) depending on the number of Igla missiles in it.
Another fundamental difference between the Strelets and the Igla-S is that the targeting and control system of the Igla is located on the launcher tube, while the control instruments of the Strelets are removed from the launching sector.
They are connected with the launcher by shielded electric cables or can be located in the cabin of the vehicle, the turret of the armored car, on a helicopter control panel or on the bridge of a patrol boat.
According to the designers, the Strelets launcher with a missile but without controls would be useless, including for terrorists, as targeting becomes impossible.