The $1 billion project Russia is building under a 1995 contract was put in jeopardy after it said that Tehran had not made any payments for the NPP's construction since mid-January, and that by the fourth quarter of 2006 the project had only received 60% of the required funding.
"Construction completion terms were coordinated in December of last year. And the Russian side worked according to schedule until financial and technical conflicts occurred," Igor Ivanov told a RIA Novosti news conference.
He said the issue is being discussed between experts, as the problem is not political.
"It is clear the schedule will have to be changed. It is hard to say for me by how many months, because the negotiations are ongoing," Ivanov said.
On March 26, Atomstroyexport announced that Tehran had resumed financing of the Bushehr nuclear power plant and that it had received the first payment from Iran, but reiterated that Russia expected future payments on time to avoid further construction delays.
The Bushehr project implemented under the supervision of the UN nuclear watchdog was originally to be commissioned at the end of 2006, but the date has been postponed five times.
The project was originally started by Germany's Siemens in 1975, but work stopped following the 1979 Islamic Revolution.
The UN Security Council voted unanimously March 24 to impose new sanctions against the Islamic Republic for its refusal to halt uranium enrichment, which the country resumed in January 2006 for what it claims to be a civilian nuclear power generating program.
The program has met fierce opposition in the West, particularly the United States, which suspects Iran is pursuing a covert nuclear weapons program.