Irina Yesipova, a spokeswoman for state-run Atomstroiexport, said the company has not received payments from Iran for two months.
Atomstroiexport said in a statement Russia will not deliver uranium fuel this month as earlier planned. The plant was scheduled to begin operations in September 2006.
The announcement follows failed talks between Atomstroiexport and the Atomic Energy Organization of Iran last week in Moscow.
Atomstroiexport officials traveled to Tehran today for a fresh round of talks.
Tehran has warned Russia not to politicize the issue and not to link the project with the international dispute over Iran's nuclear program.
(compiled from agency reports)