Western diplomats said a joint letter from the big three European foreign ministers - Jack Straw of the UK, Dominique de Villepin of France and Joschka Fischer of Germany - the content of which has not previously been disclosed, was delivered to Tehran in early August despite intense lobbying by Washington.

It highlighted a gulf between the administration of US President George Bush and even its closest European ally, Britain, on whether to engage or isolate the Islamic republic.

The Europeans urged Iran to sign, implement and ratify the Additional Protocol to the nuclear Non-Proliferation Treaty (NPT) that provides for intrusive, short-notice inspections and to halt its uranium enrichment programme, which Western governments fear could be at the heart of a clandestine nuclear arms programme.

Transatlantic split

In return for compliance, the letter raised the prospect of cooperation on technology, without specifically pledging help with a civilian nuclear energy programme, the sources said.

"Washington did not consider it very helpful at all. They were worried it ran the risk of splitting Europe and America on this issue, and they talked to their friends and colleagues in Europe about that and attempted to dissuade them from sending the letter," a diplomat familiar with the exchanges said.

"There was no offer in return. There has been no quid pro quo"

French Foreign Ministry spokesman

In Washington, State Department spokeswoman Brenda Greenberg said there was no immediate comment on the reported offer to Iran, on a day the federal government remained closed in the aftermath of Hurricane Isabel.

A French Foreign Ministry spokesman said he could confirm a letter had been sent to Iran, calling on it to sign the Additional Protocol. But he said it did not include any offer to cooperate on other issues. "There was no offer in return," he said. "There has been no quid pro quo."

European diplomats said they were disappointed there had not been a more specific reply from Tehran so far.

Extraordinary humiliation

In Tehran, a leading cleric said on Friday Iran should consider quitting the NPT after the UN's nuclear watchdog - the International Atomic Energy Agency (IAEA) - set an 31 October deadline for Iran to prove it is not seeking atomic weapons.

"What is wrong with considering this treaty on nuclear energy and pulling out of it? North Korea pulled out of it and many countries have never entered it," Ayat Allah Ahmad Jannati told worshippers at Friday prayers at Tehran University.

The IAEA gave Tehran an ultimatum last week to prove by 31 October it has no secret weapons programme or be reported to the Security Council for possible sanctions.

Jannati, head of the powerful supervisory body the Guardian Council, also said the Additional Protocol "would impose an extraordinary humiliation on us and we should never accept it".

Conservatives regard international inspections of the nuclear programme as tantamount to allowing spies into Iran - which says its nuclear programme is purely to meet booming demand for electricity.

Pledges

The reformist government of President Muhammad Khatami has however said it will continue to negotiate with the IAEA and will not pull out of the NPT.

On 18 August, Khatami wrote a general letter to European leaders, including EU president Italy, pledging that Iran would never divert its civilian nuclear programme for military purposes and had decided to enter immediate talks on the Additional Protocol.

But that message, seen by Reuters news agency, did not commit Iran to sign or ratify the protocol, and European diplomats question whether Khatami, locked in a power struggle with Islamist clerics, has effective control over the nuclear programme.
 
Since the Europeans' letter was sent, growing attention at the IAEA has focused on the need to know more about Iran's past nuclear activities as well as to enforce intrusive spot checks in future, diplomats said.

The IAEA gave Tehran an ultimatum last week to prove by 31 October it has no secret weapons programme or be reported to the Security Council for possible sanctions.

But a diplomat from one of the European states stressed that the joint British, French and German initiative remained valid.

"The offer still stands," he said.