MOSCOW - Russia's first interplanetary mission in more than two decades went awry on Wednesday when an unmanned spacecraft failed to take the proper course toward Mars after its launch, the Interfax news agency cited the head of Russian space agency Roskosmos as saying.

Roskosmos chief Vladimir Popovkin said an engine failed to fire on the Phobos-Grunt probe after it reached Earth's orbit, Interfax reported, leaving its mission to bring back a soil sample from the Mars moon Phobos in doubt.

In a forum on the mission's official website, Anton Ledkov of the Russian Space Research Institute said there was no telemetry from the craft, but Popovkin said space officials were in contract with it and had three days to set it on course before the batteries run out, Interfax reported.

"The engine did not fire, neither the first nor the second burn occurred. This means that the craft was unable to find its bearings by the stars," the agency quoted him as saying.