MOSCOW -- Some recent Russian satellite failures may have been the result of sabotage by foreign forces, Russia's space chief said Tuesday, in comments apparently aimed at the United States.

Roscosmos chief Vladimir Popovkin stopped short of accusing any specific country of disabling Russian satellites, but he told the daily Izvestia that some Russian craft had suffered "unexplained" malfunctions while flying over another side of the globe beyond the reach of his nation's tracking facilities.

Popovkin spoke when asked about the failure of the $170-million unmanned Phobos-Ground probe, which was to explore one of Mars' two moons, Phobos, but became stranded while orbiting Earth after its Nov. 9 launch.

Engineers in Russia and the European Space Agency have failed to propel the spacecraft toward Mars, and it is expected to fall back to Earth around Jan. 15.

Popovkin said modern technology makes spacecraft vulnerable to foreign influences.

"I wouldn't like to accuse anyone, but today there exists powerful means to influence spacecraft, and their use can't be excluded," he said.

James Oberg, a NASA veteran who has written books on the Russian space program, said Popovkin's comments were a sad example of the Russian cultural instinct to "blame foreigners."