MOSCOW (Reuters) - Russia's first planned interplanetary mission in more than two decades went wrong on Wednesday when a $163 million unmanned spacecraft failed to take the proper course toward Mars soon after its launch.

Russian space agency chief Vladimir Popovkin said an engine failed to fire on the Phobos-Grunt probe after it reached Earth's orbit, leaving Moscow space officials just three days to jolt it out of orbit before its batteries run out.

"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," state television quoted Popovkin as saying at Russia's Baikonur launch facility in Kazakhstan.

The mission to bring back a sample of soil -- "grunt" in Russian -- from the Martian moon Phobos was supposed to assert Russia's place at the front line of space exploration.

But if Moscow cannot bounce it out of orbit, the Phobos probe could become several tonnes of expensive space junk circling the Earth.

Failure would be a major blow to the pride of Russia's space agency, which was crimped by budget constraints and a brain drain following the 1991 Soviet collapse and suffered a humiliating series of setbacks this year.

"They say there is hope to reset it, apparently it's a problem with the programing but there is very little time," the lead mission scientist Alexander Zakharov of the Space Research Institute told Reuters.

"I feel grief. It's very sad that this is how it all worked out but this is a consequence of our lack of people after such a big interval... Many young people worked on this. There is a lack of experience, we are working almost from scratch."

COSTLY MISSION

The 5-billion-rouble ($163 million) probe blasted off at 12:16 a.m. Moscow time (3:16 p.m. ET Tuesday) from the Baikonur launch pad on a Zenit-2SB rocket, Roskosmos said -- starting what is meant to be a three-year trip to Phobos and back.

It was an undertaking haunted by past failures, and has become a test of the Russian space industry. If successful, its long journey would be the first Soviet or Russian deep-space probe to Mars to fulfill its mission completely.

Six men have also just completed a 520-day experiment in Russia intended to help show whether people could stay healthy and sane if they went to Mars and back.

Meanwhile, U.S. rovers have logged hundreds of hours on Mars, India and China have sent probes to Earth's moon, while Japan has visited an asteroid and brought back samples.

Russian scientists have dreamed of probing the Red Planet's potato-shaped satellite Phobos, a mere 22 km (13 miles) across, since the 1960s heyday of pioneering Soviet forays into space.

But two Phobos missions sent up in 1988 failed, one going silent within meters of the surface. In 1996, another unmanned Russian craft bound for Mars broke up in the atmosphere after a botched launch.

"We have always been very unlucky with Mars," Zakharov said.

Moscow's last successful missions beyond Earth orbit, Vega 1 and 2, probed Venus and Halley's Comet in the mid-1980s.

Russia continues to ferry astronauts to the International Space Station, but a series of failed unmanned launches this year has underscored the fragility of its space program.

Dust from Phobos, scientists say, could shed light on the genesis of the solar system, and data collected on the voyage might help solve enduring mysteries such as whether Earth's neighbor has ever supported life.

The plan is for Phobos-Grunt to reach Mars next year, touch down on the larger of Mars' two tiny moons in 2013, collect a sample from the surface and fly back to Earth in 2014.

Hitching a ride is China's first interplanetary spacecraft, the tiny 115-kg (250-pound) Yinghuo-1, which is to work in orbit with Phobos-Grunt over a year to study the atmosphere of Mars.

Phobos-Grunt is also carrying vials of Earth bacteria suited to extreme environments, plant seeds and tiny invertebrate animals known as water bears, to see if they can survive in space.

It is meant to be the first time microbes carried by a spacecraft spend years in space and go beyond the protective bubble of Earth's magnetic field, testing part of a theory that life may have migrated between planets inside meteorites.

(Additional reporting by Steve Gutterman and Guy Faulconbridge; Editing by Peter Graff)