Iran has agreed to sign up to tougher United Nations inspections of its nuclear facilities and to suspend its enrichment of uranium.
An important step in resolving the nuclear issue, the EU ministers said
The breakthrough came as European Union foreign ministers held intensive negotiations in Tehran on ways to defuse the crisis over Iran's alleged nuclear programme.
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 - described Tuesday's result as "an encouraging sign".
The White House also said Iran's decisions would be a "positive step" if implemented.
In a joint declaration with the visiting ministers, Iran promised full co-operation with the IAEA and said it would sign the additional protocol of the Nuclear Non-Proliferation Treaty (NPT).
This would allow UN inspectors to carry out spot checks of Iranian facilities.
The Iranians also said they would suspend all their uranium enrichment activities and reprocessing of uranium fuel, in line with an IAEA request.
"The Iranian authorities reaffirmed that nuclear weapons have no place in Iran's defence doctrine," the statement added.
The BBC's Jim Muir in Tehran says that on paper at least this means Iran is complying fully with the IAEA demands, the Europeans and even the Americans.
The British, French and German foreign ministers in return recognised Iran's right "to the peaceful use of nuclear energy".
Provided Iran met international concerns, the Islamic Republic "could expect easier access to modern technology and supplies in a range of areas," the declaration said.
"This is, we hope, a promising start in which everyone has to play their part," French Foreign Minister Dominique de Villepin said.
His sentiments were echoed by Joschka Fischer of Germany and the UK's Jack Straw. But Mr Straw also stressed that 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.
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".
Tehran denies it has a nuclear weapons programme
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.