The secretary of Iran's powerful Supreme National Security Council, Hasan Rowhani, said Iran would sign an additional protocol to the Nuclear Nonproliferation Treaty that would allow inspectors to enter any site they deem fit without notice.
"The protocol should not threaten our national security, national interests and national pride," he told reporters.
He added that for an "interim period," Iran will suspend nuclear enrichment "to express its goodwill and create a new atmosphere of trust and confidence between Iran and the international community."
There was no indication of when Iran would suspend its uranium enrichment or sign the additional protocol, and Rowhani did not say how long the interim period would last.
Jack Straw of Britain, Joschka Fischer of Germany and Dominique de Villepin of France were here to press Iran to meet an Oct. 31 deadline set by the International Atomic Energy Agency for proving it does not have a nuclear weapons program.
The United States strongly believes Iran is trying to develop nuclear weapons, though Tehran insists its nuclear program aims is designed only for producing energy. Iran has allowed IAEA inspectors to view some sites, including at least one military facility — but for weeks it has balked at making a full commitment to the IAEA demands.
In recent weeks, Iran has twice had to acknowledge that particles of uranium, enriched to weapons-grade level, have been found in different parts of the country. Iran said the particles came from contaminated equipment imported from another country it did not identify.
Some Iranian hard-liners have called for the country to quit the Nuclear Non-Proliferation Treaty.
But Iran is keen to stop the dispute from reaching the Security Council. If Iran fails to satisfy the U.N. nuclear agency, the IAEA is expected to refer the matter to the council, which could impose sanctions on the country.
In a joint statement after their talks, the three European foreign ministers recognized Iran's right "to enjoy peaceful use of nuclear energy in accordance with the Nonproliferation Treaty."
France, Britain and Germany agreed that "the full implementation of Iran's decisions, confirmed by the IAEA director general, should enable the immediate situation to be resolved by the IAEA board," the statement said.
The statement added: "Once international concerns, including those of the three governments, are fully resolved Iran could expect easier access to modern technology and supplies in a range of areas."
"It is an important day for Europe because we are dealing here with a major issue. We are talking about proliferation, which as everyone knows, is a huge challenge to the world community," de Villepin told reporters.
De Villepin said they had achieved important progress on the three pending issues: signing and the early implementation of the additional protocol, full cooperation with the IAEA, and suspension of all enrichment and reprocessing activities.
Iran has said it is prepared to grant unfettered access to IAEA inspectors, but it wants to be able to buy advanced nuclear technology. Iran accuses the United States of using its influence to block such purchases.
Straw had spoken with Secretary of State Colin Powell about Tuesday's meeting. Unlike the U.S. administration, which has characterized Iran as being part of an "axis of evil," London has sought to engage Tehran's hard-line regime. Tuesday's visit was Straw's fifth to Iran since becoming foreign secretary.
In late June, Britain, France and Germany began discussing the possibility of approaching Iranian officials together, and sent Tehran a joint letter the following month urging the regime to comply with the Nuclear Nonproliferation Treaty, of which it is a signatory.
Tehran invited the three European ministers in early October and, after a series of discussions, Straw, de Villepin and Fischer accepted the offer.
The nuclear dispute is only one area of friction between the United States and Iran. The U.S. considers Tehran a sponsor of terrorism against Israel, and some officials have accused the regime of sheltering al Qaeda leaders who have directed attacks in Saudi Arabia.
After the fall of Saddam Hussein in neighboring Iraq, U.S. officials accused Iran of trying to destabilize the country by infiltrating the large Shiite community.
Some conservative adviser close to U.S. policymakers have advocated regime change in Iran. Tehran was furious when, in the wake of the Iraq war, the U.S. briefly maintained a cease-fire with a group based in Iraq whose aim is to overthrow the Iranian regime. The group, called the Mujahadeen al Khalq, is on the U.S, list of foreign terrorist organizations.