Space launch operator Arianespace said on Monday that Europe had decided against hoisting two more Galileo geolocation satellites in December following a launch mishap in August.

Two Galileo satellites, part of an orbiting constellation scheduled to completed by 2020, were to have been launched from Kourou, French Guiana, by a Russian Soyuz rocket.

Instead, the December 18 launch will take aloft four satellites for the Internet data provider O3b Networks Ltd.

On August 22, Galileo satellites Sat-5 and Sat-6 were placed in the wrong orbit by a Soyuz launched from Europe's space base.

They should have been slotted into a circular orbit at an altitude of 23,500 kilometres (14,600 miles), inclined at 56 degrees to the equator.

Instead, they were placed in an elliptical orbit at a height of 17,000 kilometres -- a position that experts say makes them useless for satnav work.

The European Space Agency (ESA) "wants additional time to test the two Galileo satellites before resuming deployment" of the constellation, an Arianespace spokesman told AFP, without giving details.

The August 22 hitch has been pinned to frozen fuel pipes on board the launcher's fourth stage, called Fregat.

Pipes containing hydrazine propellant had been placed too close to super-cold helium feed lines, investigators reported on October 8.

Europe's 7-billion-euro (8.9-billion-euro) rival to America's GPS, Galileo has encountered a long series of technical hitches and budget questions.

By 2017, according to the Galileo schedule, all 24 operational satellites should be in place. Six backups would join the fleet by 2020, at which point the system would be fully operational.