TOKYO (REUTERS) - Japan on Saturday (Aug 12) postponed the planned launch of an H-2A rocket tasked to put a geo-positioning satellite into orbit, due to possible helium gas leakage, Mitsubishi Heavy Industries (MHI) said.

MHI, commissioned by the government to carry the satellite into space, postponed Saturday's launch after detecting a decline in pressure levels inside a tank containing helium gas, which is used to operate valves for cooling rocket engines.

The company is looking into what specifically caused the pressure decline, and the rocket is now likely to be launched as early as Aug 17, a MHI spokesman said.

The launch of a third geo-positioning satellite is part of Japan's plan to build a local version of the US global positioning system (GPS) aimed to offer location information for autopiloting of cars and possible national security purposes.

Japan plans to put into space a fourth geo-positioning satellite by the end of the year to start offering precise position information next April, using signals from the four Japanese satellites as well as US GPS satellites and others.

The US GPS has a margin of error of up to 10m, but under the new Japanese system, positioning error will come down to 6cm or less, according to the Cabinet Office.