MOSCOW, June 4 (RIA Novosti) - The number of operational satellites in Russia's Glonass grouping has been increased to 17 while three more remain inactive, Russia's Federal Space Agency Roscosmos said on Thursday.

Glonass - the Global Navigation Satellite System - is the Russian equivalent of the U.S. Global Positioning System, or GPS, and is designed for both military and civilian use. Both systems allow users to determine their positions to within a few meters.

"According to Glonass information center, one of the four satellites under maintenance was added to the grouping on May 30," Roscosmos said in a statement on its website.

"As of June 1, the Glonass system comprises 20 satellites. A total of 17 satellites are operational while three remain under maintenance," the statement said.

The system requires 18 satellites for continuous navigation services covering the entire territory of the Russian Federation, and 24 satellites to provide services worldwide.

A total of 9.9 billion rubles ($360 million at the current exchange rate) was allocated for Glonass from the federal budget in 2007, and 4.7 billion rubles ($170 million) in 2006.

Prime Minister Vladimir Putin signed a directive on September 12, 2008, allocating an additional $2.6 billion to develop the system.

Two Proton-M launch vehicles are expected to lift off this year to put six more Glonass-M satellites into orbit.