Russian specialists are completing the construction of Iran's first NPP under a $1 billion contract signed in 1995, but Russia claimed last month that Iran had an unpaid debt for its construction services, and said that as a result construction might take longer than previously expected.
The official said the sides had released no joint statement despite earlier promises, and added the Iranians had failed to meet any of the obligations assumed in September.
"The financing of the project in 2007 had come to a virtual halt as well as equipment supplies from third countries," the source said.
On Wednesday Iranian Foreign Minister Manouchehr Mottaki said that Iranian payments had been made ahead of schedule adding that construction was almost complete and that suspending or freezing the project was out of the question.
The Russian source said he was surprised with statements of some Iranian high-ranking officials that there were no problems with financing of the Bushehr construction.
"We can assume that Iran's high-ranking officials are not fully informed about the construction progress," he said. "But when it comes from our vis-a-vis present at the talks, who is fully aware of the state of affairs, we are somewhat surprised."
Mohammad Saidi, deputy director of Iran's Atomic Energy Agency, who led the Iranian delegation at the talks in Moscow, said in turn to Iran's IRNA information agency that the talks were constructive and next week the Russian delegation will arrive in Tehran to complete negotiations.
"We discussed the financial issues at the talks in Moscow, which had emerged with the Russian company Atomstroyexport," Saidi said. "We have agreed that next week the Russian delegation will visit Tehran to discuss the details."
The Bushehr facility has been a source of international dispute, with the United States and other Western countries raising concerns that Iran could use the project as part of a covert weapons program. Iran has consistently denied that its nuclear program has military goals.
The UN Security Council adopted a resolution in December imposing sanctions against Iran.
Russia, a key economic partner of Iran, has consistently supported the Islamic Republic's right to nuclear power under the Nuclear Non-Proliferation Treaty (NPT), and has resisted the imposition of harsh sanctions.
