By Olly Bootle
Assistant producer, Iran's Nuclear Secrets
The unearthing of nuclear facilities in Iran, concealed from the outside world for 18 years, has reinforced the United States' suspicion of the Islamic state, but is it too late for international arbitration?
Can diplomacy end the mutual distrust between Iran and the West?
Three months ago, reporter Paul Kenyon and I received visas to go to Iran.
After much negotiation, Iran's Atomic Energy Organisation had agreed to help us make a documentary about the state of their nuclear programme.
With the threats from America and Israel piling up, and the window for a diplomatic solution with the Europeans slowly shutting, the Iranians were keen to tell their side of the nuclear story.
That story is simple: they have a peaceful nuclear energy programme, and according to the Nuclear Non-Proliferation Treaty (NPT), they have an "inalienable right" to develop and use nuclear technology for peaceful means.
The American story is equally simple. As Assistant Secretary of State for Arms Control Stephen Rademaker told us: "We think there's no question that Iran has embarked on a project to acquire nuclear weapons."
The Americans' suspicion, shared by many Western countries, is due to the fact that for 18 years Iran was developing a nuclear programme that they kept largely hidden from the world, by obtaining resources on the black market and burying facilities underground.
It was only a couple of years ago, when an Iranian opposition group exposed the secret programme, that the world discovered the extent of it.
But Ali Akbar Salehi, Iran's former ambassador to the UN's nuclear agency, was very clear about why Iran had to keep secrets.
"It is because of the sanctions, the international sanctions," he says. "I mean engage with Iran and see how Iran behaves."
The United States, however, is not willing to engage. Instead, it has imposed sanctions on Iran for over two decades, and wants the UN Security Council to deal with the "rogue state's" nuclear programme.
Lack of proof
The problem for the US though, is that there is no solid evidence that the Iranians have a military nuclear programme.
President Khatami insists Iran has a right to nuclear power
As Mohamed ElBaradei, head of the UN's International Atomic Energy Agency (IAEA), told us: "We haven't seen a smoking gun. We haven't seen material diverted to nuclear weapons."
But Mr Rademaker does not like this cautious approach.
Of the IAEA's assessments of Iran's programme he says: "Those reports are written in very diplomatic language... any objective reader who reads a paragraph understands that Iran lied about issue after issue after issue."
While the US wants to see Iran dealt with by the UN Security Council, Mr ElBaradei does not want to close the diplomatic door in Iran's face.
If the talking stops, Iran could withdraw from international treaties, and then Mr ElBaradei's nuclear inspectors have no right to go to Iran to keep an eye on their programme.
This is what happened with North Korea a few years ago, and now they claim to have the bomb.
Unlike North Korea though, Iran is still a member of the NPT and the IAEA. The nuclear inspectors travel there every month to verify that Iran is not doing anything it should not be doing.
We were told we would be arrested if we went anywhere near certain nuclear facilities
And so in February of this year, we travelled there with them.
The so-called transparency was not quite what we had hoped for. We were told that we could not accompany the inspectors inside any of the nuclear facilities for security reasons.
But the president of Iran's Atomic Energy Organisation - who also happens to be vice president of the country - did give us permission to film outside nuclear facilities.
In Iran however, things are never quite that simple.
By the end of our trip, we were being followed by the country's intelligence services, told we would be arrested if we went anywhere near certain nuclear facilities, and even prevented from driving around with the inspectors.
Despite our journalist visas, a letter of accreditation to film, and permission from the vice president, the intelligence services apprehended us as we were about to leave the country and confiscated more than half of our tapes.
While this may seem to suggest they have something to hide, anyone who knows Iran will tell you it is a deeply divided country.
The reformists seek reconciliation with the West, and so they let us into the country, while the conservatives are happy to be distrusted by the outside world because it encourages the nationalism that consolidates their domestic power base.
But Iran's nuclear story has reached a decisive chapter.
Iran's Atomic Energy Organisation is under intense scrutiny
The Iranians have agreed to temporarily suspend key aspects of their nuclear programme, in order to build confidence with the West.
When we asked Ali Akbar Salehi if Iran would agree to maintain this suspension permanently, he immediately replied: "No... these are the red lines that have been drawn by the Supreme Leader."
The West, on the other hand, is adamant that it cannot allow Iran to have a nuclear enrichment programme, as it brings them alarmingly close to weapons capability.
Mr Rademaker made it very clear. He says: "The position of the US is that we want complete cessation and dismantlement of the enrichment programme in Iran."
Neither side is willing to budge.
The only thing stopping Iran from recommencing their enrichment programme, and thus facing immediate US reprisals, is the fact that the Europeans are trying to find a diplomatic solution.
But with the Europeans currently agreeing with the US, and with Iran already saying that they will not allow the suspension to continue for more than a few more months, it is hard to see how this equation can be solved without a visit to the Security Council.
Iran's Nuclear Secrets was broadcast on Tuesday, 3 May, 2005 at 2100 BST on BBC Two.