The United States said this afternoon that Iran's agreement to freeze uranium enrichment could be a positive step if fully carried out.
"Full compliance will now be essential," White House spokesman Mr Scott McClellan, who is with US President George W Bush on an Asian tour, told reporters.
The US comment followed the announcement that Iran had agreed to accept tighter nuclear inspections and suspend its uranium enrichment. US officials have suspected Iran has been trying to develop nuclear weapons, a charge denied by Tehran.
Mr McClellan said the Iranian move would be positive if the Iranians sign a protocol allowing more intrusive inspections, if they cooperate fully with the International Atomic Energy Agency and end uranium enrichment and reprocessing.
If all that happens, he said, "it would be a positive step in the right direction."
Mr McClellan thanked Britain, Germany and France for their role in coaxing the agreement from Iran, which Mr Bush had referred to as part of an "axis of evil" along with Iraq under Saddam Hussein and North Korea, rogue nations he said were bent on developing weapons of mass destruction.
"We have been in close contact with the Europeans all along so we very much welcome the efforts by the British, German and French foreign ministers to obtain a commitment of full compliance by Iran with its IAEA and non-proliferation obligations," Mr McClellan said.