MOSCOW, May 13 (RIA Novosti) - Russia's state arms exporter Rosoboronexport is preparing a $4 billion arms contract with Saudi Arabia, the Gazeta daily reported on Tuesday.

A preliminary agreement on the purchase of Russian weaponry was reached in November 2007, during a meeting between then-president Vladimir Putin and Crown Prince Sultan Ibn Abdel Aziz Al Saud in the Kremlin.

Riyadh reportedly intends to buy 150 T-90S main battle tanks, worth around $500 mln, a large consignment of BMP-3 infantry fighting vehicles, over 100 Mi-35 (Hind) transport/attack and Mi-17 (Hip) multirole helicopters, and around 20 Buk M2E surface-to-air medium-range missile systems.

Experts say the helicopter contract alone is worth around $2 billion.

Even if the deal with Saudi Arabia goes ahead, it is just a drop in the ocean compared to the market share enjoyed by the U.S. and the U.K., who jointly control 90% of Saudi arms purchases.

The arms contract with the Saudis could also boost Russia's admission to the World Trade Organization. During ongoing bilateral negotiations with Moscow, Riyadh demanded access to Russian hydrocarbon deposits and pipelines.

Moscow's chief WTO negotiator Maxim Medvedkov said recently an agreement with Riyadh could be finalized in June.