Russia's state space corporation, Roskosmos, said an "abnormal situation" occurred as mission control tried to move the craft into a pre-landing orbit at 11:10 GMT on Saturday, ahead of a planned touchdown slated for Monday.
"During the operation, an abnormal situation occurred on board the automatic station, which did not allow the manoeuvre to be performed with the specified parameters," Roskosmos said in a short statement.
Russia has not attempted a moon mission since Luna-24 in 1976, when Leonid Brezhnev ruled the Kremlin.
Luna-25 was supposed to execute a soft landing on the south pole of the moon on Aug. 21, according to Russian space officials.
It was not immediately clear from official sources how serious the "abnormal situation" was - and whether or not Moscow could save the situation.
Persons:
Luna, Roskosmos, Yuri Gagarin, Leonid Brezhnev, Alexander Ivanov, Guy Faulconbridge, Christina Fincher
Organizations:
REUTERS, Kremlin, India, Thomson
Locations:
Handout, MOSCOW, Moscow, Soviet, Russia, China, United States, Ukraine