The head of Russia's federal agency for atomic energy Rosatom, Sergei Kiriyenko, said the timetable for Russian contractors to complete the Bushehr plant in the south of Iran would depend on timely and full payments.

"When the payments are adequate, work is not interrupted," Kiriyenko was quoted by a spokesman as saying. "For the moment I would not call them adequate."

"For now it is premature to talk of a specific time frame for the construction of the Bushehr nuclear power station," Kiriyenko was quoted as saying.

The completion of the power station, which is 95 percent ready, and the delivery of nuclear fuel by Russia, planned for this year, have been delayed by what Moscow described earlier as financial problems.

Iran has been under pressure from the United States and the European Union to freeze its civilian nuclear programme and Washington has called on Moscow to halt construction of Bushehr.