The State Department said no nation, including Russia, should be assisting Iran in its nuclear efforts until Tehran agrees to allow snap inspections of its installations by the IAEA which has raised concerns about the scope of the program.
"Until Iran satisfies the IAEA's questions and fully addresses the concerns of the international community ... we believe that no country should be engaging with Iran in nuclear cooperation, and that would include Russia," deputy spokesman Philip Reeker said.
Among other things, this would entail Iran's "full, immediate, unconditional implementation of the additional protocol to the (nuclear) Non-Proliferation Treaty," he told reporters.
That additional protocol, which would allow for surprise and intrusive inspections, is to be discussed by the IAEA's governing board when it meets in Vienna to review a report on Iran's nuclear program.
Reeker's comments came in response to questions about reports Moscow may soon sign a deal with Tehran regarding the return of spent nuclear fuel that would pave the way for the launch in 2004 of Iran's first atomic reactor.
The agreement regarding Iran's Bushehr nuclear power plant, now under construction by Russia, could be signed at the IAEA meeting, according to Russian officials.
Those officials spoke following a two-day visit to Moscow of the top US arms control diplomat, John Bolton, who renewed US complaints about Russian-Iranian nuclear cooperation.
The United States believes Iran's nuclear program is a cover for clandestine atomic weapons development.
Iran has vehemently denied the US charges, insisting its nuclear activities are energy-related, and has said it is ready to begin talks on signing the additional protocol to the NPT.
But it has said it will not sign the agreement unless it first receives guarantees that IAEA inspectors would not be given complete freedom of movement and would not violate military secrets.
The IAEA board is to begun discussing the Iran report on September 8 and could refer the matter to the UN Security Council for a possible consideration of sanctions.