The announcement by Iran that it will take steps to allay international concern over its nuclear programme has been favourably received around the world.
Iran has allayed international fears over its programme - for now
Iran said earlier on Tuesday that it would sign an additional protocol to the Nuclear Non-Proliferation Treaty, which would pave the way for tougher UN inspections of its nuclear facilities.
In a guarded welcome, the White House said Iran's offer, if carried out, would be a "positive step".
The Vienna-based International Atomic Energy Agency (IAEA) - which had given Iran until 31 October to provide evidence that it is not trying to build nuclear weapons - also said the agreement was "an encouraging sign".
In a joint declaration with visiting EU ministers who held intensive negotiations in Tehran, Iran promised full co-operation with the IAEA and said it would sign and implement the additional protocol of the Nuclear Non-Proliferation Treaty (NPT).
Speaking after talks with the foreign ministers of Britain, France and Germany, Iranian diplomats said Tehran would also voluntarily suspend all its uranium enrichment and reprocessing activities, in line with a resolution by the IAEA.
IAEA spokesman Mark Gwazdecki said access to information was key to implementing the accord.
"What we are trying to do is reconstruct the history of a nuclear programme that goes back almost 20 years," he told the BBC's Newshour programme.
"We are going to do that through getting information from the Iranian Government and verifying its accuracy and completeness. We can only do so much by actually visiting sites. The rest of it needs to come from the Iranians themselves."
The White House spokesman, Scott McClellan, stressed that Iran should now sign an agreement allowing more intrusive inspections.
"What is important now is not only the words
by the Iranians, but the action to fully implement what their international obligations are," he said.
UK Foreign Minister Jack Straw echoed the US words of caution, saying everything depended on Iran fulfilling its promise.
"The proof of the value of today will depend not just on the words in the communique... but above all on the implementation of what has been agreed," he said.
But the BBC's Jon Leyne says the statement poses a dilemma for the Bush administration that has labelled Iran a member of the axis of evil.
The US view, our correspondent says, has always been that a nation with Iran's oil reserves has no need of any nuclear reactors, even for a civilian programme.
And Washington also wants to avoid the Iranian Government driving a wedge between the United States and the European countries which secured this agreement.
The head of Iran's powerful National Security Council, Hassan Rohani, said the decision to suspend the uranium enrichment programme was a temporary measure aimed at fostering trust in Iran's peaceful intentions.
"We voluntarily chose to do it which means it could last for one day or one year, it depends on us," Mr Rohani was quoted as saying by Reuters news agency.
"As long as Iran thinks that this suspension is beneficial for us it will continue and whenever we don't want it we will end it."
Mr Rohani added that he did not expect they would sign the additional protocol before 31 October but "probably before 20 November".