In what could be a breakthrough just 10 days before the expiry of an International Atomic Energy Agency (IAEA) deadline telling Iran to come clean on its nuclear activities, a top Iranian official also said talks with the UN's nuclear watchdog had yielded an "understanding" on reinforced inspections.
"We found a mutual understanding," Iran's representative to the IAEA, Ali Akbar Salehi, told AFP after what he described as two days of "intensive negotiations" with IAEA experts.
He said Iran "now has a more positive stance" towards signing the additional protocol of the Non-Proliferation Treaty (NPT) -- which would give the green light to the IAEA to carry out surprise inspections of suspect facilities.
Salehi said it was now up to the Iranian leadership to make a final decision on the additional protocol -- a key demand of the Vienna-based IAEA -- and added he expected them to decide in "a matter of days or weeks".
The IAEA decided in September to set an October 31 deadline for Tehran to allow tougher inspections of its nuclear programme and answer widespread fears it may be secretly developing atomic arms.
Salehi said Iran would also satisfy the IAEA's demands for answers to a number of "outstanding issues" -- in other words serious questions sparked by the discovery here of highly enriched uranium by IAEA inspectors.
Signs of breakthrough in the often bitter stand-off were coupled with Britain, France and Germany taking the cover off a frantic and secretive diplomatic bid aimed at defusing the crisis peacefully.
Their capital's confirmed that Jack Straw of Britain, France's Dominique de Villepin and Germany's Joschka Fischer would be in Tehran for talks on Tuesday.
Diplomats say the European Union's big three have for months been engaged in an effort to convince Iran to fully comply with IAEA demands, and say they were unlikely to make such an unprecedented joint visit unless they were certain of some success in ending the current crisis.
Iranian officials said the foreign ministers would be meeting with President Mohammad Khatami. Straw has made no less than five visits to Iran in just two years, de Villepin visited earlier this year and Fischer was in Iran in 2000.
While the German foreign ministry said the three would "make clear" concern over Iran's nuclear programme, the French set the tone of high expectations by noting "the Iranian authorities now seem prepared to announce a certain number of confidence-building measures aimed at the international community."
In return for Iranian compliance, the three are believed to have offered technical assistance, and possibly supplies of nuclear fuel in order to satisfy Iran's desire for nuclear power while keeping the sensitive nuclear fuel cycle -- and the risks to proliferation it entails -- out of the country.
Iran denies it is developing nuclear weapons, but the IAEA says its inspectors need the extra powers provided by the additional protocol to fully verify and accurately report on a nuclear energy programme that Washington suspects is a cover for a drive to acquire an atomic bomb.
Only Russia is helping Iran's energy programme, and Iran complains it has has been denied assistance due to US sanctions -- even though it is a signatory of the NPT.
Diplomats say that while Washington has deep reservations over the European diplomatic effort, it recognises it can not be assured of winning an international consensus if Iran does not meet the IAEA deadline of October 31 and the dossier is passed to the UN Security Council for possible sanctions.
And while there has even been speculation of possible US or Israeli strikes against Iranian nuclear facilities, analysts also point to the United States' ongoing woes in Iraq as good reason for leaving room for diplomacy -- as it has done with other "axis of evil" member North Korea.
While Iran has never ruled out signing the additional protocol, it has expressed concern that giving the UN watchdog access to its facilities -- many of them sensitive and key to national security -- would represent a surrender of sovereignty.
Some of Iran's powerful hardliners have even suggested following the example of North Korea and pulling out of the NPT altogether.