Russia to 'restrict' US-run GPS satellites
Russian authorities have "implemented measures" to restrict the use of satellite bases in its territories that serve the US-owned GPS network.
The country's space agency said it would rule out "any military use" of the ground-based stations.
The move comes amid Russian attempts to build a US base for its GPS rival, the navigation system Glonass, which have been blocked by the US government.
However experts say the move will have no effect on GPS users worldwide.
GPS bases in Russia will be "stopped completely," if an agreement on Glonass stations in the US is not reached by 31 August, warned deputy prime minister, Dmitriy Rogozin.
GPS (Global Positioning System) is a satellite navigation network owned and run by the US government.
It is used to provide accurate positioning for both civilian and military devices.
Ground-based monitor stations feed back geodesic information to space, which improves the system's accuracy.
In a statement, Russia's Federal Space Agency, Roskosmos, said it would "rule out" the use of information from network stations operating on the signals of the GPS system and located in the Russian Federation, "for purposes not covered by existing agreements, including military uses".
However, experts say the move will have a minimal effect, if any, on GPS users worldwide, with a possible loss of accuracy for some users in Russia.
Prof David Last, a consultant on navigation systems and previous president of the Royal Institute of Navigation, told the BBC the US "does not depend for the command and control of GPS on monitoring stations in Russia".
While there are a handful of stations around the world which monitor GPS under US government control, Russia only hosts smaller Continuously Operating Reference Stations (Cors), which primarily provide meteorological data and monitor earthquakes, but also feed some data to GPS satellites
"Their purpose is to increase reliability [of GPS] for local users," said Prof Last.
"Closing them will only have an effect on GPS users in Russia."
Cors are independently owned and run.
Russia's Glonass, which was established in the late 1970s, is the only global rival to GPS, and has been subject to failures in recent months.
The country's space agency has been trying to improve the system's accuracy, and wants to put a base station for Glonass in the US - a move which has been all but ruled out by the White House.