"Our view is that people ought to be careful -- continue to be careful -- about their programs, particularly at this moment when Iran has not yet implemented all its commitments" to the International Atomic Energy Agency, State Department spokesman Richard Boucher said.
Boucher's comment was aimed at Russia, which is cooperating in the construction of Iran's Bouchehr nuclear power station on the Gulf. Washington has had Russia on notice about the plant for years.
"We never said (Russia) should stop the reactor cooperation.
"We've said that other aspects of cooperation with Iran should not be carried out and that peaceful reactor construction should proceed only if Iran was meeting all the requirements of the international community to satisfy the international community that Iran was not conducting weapons programs on the side."
Boucher pointed out that Iran had promised the UN nuclear watchdog that it would allow more intrusive inspections, but that they may not have signed or implemented the agreements.