Industry sources said the Syrian contract was signed in early 2007 and the first aircraft delivery was expected over the next few months. The sources said the MiG-31E, with a configuration similar to that ordered by India, would provide Syria with a huge leap in air combat capability.

"The Syrians will be getting the top line of Russian aircraft through financing by Iran and share some or most of the platforms with the Iranian Air Force," a Russian industry source said. "This is the start of a new era."

On Tuesday, the Moscow-based Kommersant business daily reported that Russia would deliver five MiG-31E fighters in 2007. The newspaper, which reported a series of weapons deals later acknowledged by the government of President Vladimir Putin, said the first MiG-31s would come from Russian Air Force surplus and modified to Syrian requirements.

"Export orders are starting to come in for the MiG-31," MiG deputy director-general Vladimir Vypryazhkin said without elaborating. "We are offering the MiG-31E on a trade-in basis for countries that have the MiG-25 interceptor."

Syria ordered 35 MiG-25 Foxbat aircraft in 1980. Most of them have been grounded because of Syrian difficulties in maintainance and spare parts.

Kommersant, citing Russian industry sources, said Syria signed a $1 billion contract for the MiG-31E as well as the MiG-29STM fighter. The newspaper said the deal was financed by Iran, which would share the aircraft.

Israeli military intelligence has been closely following Syrian orders of Russian aircraft. Israeli analysts believe Damascus would order at least 25 MiG-31Es, or enough to form an air force squadron.

"It makes little sense to limit oneself to five planes," Shmuel Gordon, an Israeli reserve air force colonel and a leading defense analyst, said. "Where there is five, there will soon be 20, and maybe 24 planes. Maintenance of the planes is very expensive, but it makes no difference whether you maintain five or 20 of them."