The S-400 Triumf is a new air defense missile system developed by the Almaz Central Design Bureau as an upgrade of the S-300 family. Russia first demonstrated the S-400 system at an ongoing air show outside Moscow.
"Belarus submitted a formal request for two S-400 battalions to be made available by 2010," the source said.
He said that it is too soon to talk about a specific timeframe for the contract, but if the Belarusian application is accepted and all contract terms are honored, the S-400 systems could be delivered in 2010.
Another military official said Thursday no S-400 SAM systems will be exported to any country, including the CIS, in the next few years.
"A decision to export such systems may only be made by the country's top leadership," the expert said, commenting on a recent statement by Belarus's defense minister about his country's intention to buy S-400 systems.
Almaz General Director Igor Ashurbeili said previously production and the subsequent export of S-400s could start in 2009.
Russia has deployed an S-400 battalion to protect the airspace around the capital, Moscow.
The S-400 has been designed to intercept and destroy airborne targets at a distance of up to 400 kilometers (250 miles), or twice the range of the U.S. MIM-104 Patriot, and 2.5 times that of the S-300PMU-2.
The system is believed to have high capability to destroy stealth aircraft, cruise missiles, and ballistic missiles with an effective range of up to 3,500 kilometers (2,200 miles), and a speed of up to 4.8 kilometers (3 miles) per second.
Experts believe that the ability to intercept and destroy cruise missiles and ballistic missiles makes the S-400 Triumf a crucial part of theater missile defenses.
A regular S-400 battalion comprises at least eight launchers and 32 missiles and a mobile command post, according to various sources.