Efforts by the International Atomic Energy Agency (IAEA) to get Iran to allow full inspections of its nuclear facilities are part of a desperate attempt to shore up the Nuclear Non-Proliferation Treaty which has failed to stop the spread of nuclear weapons.
The squeeze is now on to show that a country can be brought into line.
There appears to be a determination to prevent the development of the crisis which would be precipitated with the United States and Israel if Iran built the bomb. Iran's neighbour, Iraq, is seen as a warning of what can happen when the international community loses control.
Backing from European Union
The European Union threw its weight behind these efforts by linking progress on an EU-Iran trade agreement to Iranian nuclear compliance.
But Iran will not necessarily be prevented from developing nuclear weapons even if it signs up to a stricter inspections regime.
Tehran denies it has a nuclear weapons programme
In the final analysis, a country cannot be stopped from making a nuclear weapon.
India, Pakistan and Israel, for example, have done so by refusing to join the NPT and North Korea has simply left the Treaty, declaring its own nuclear ambitions.
Gary Samore, a former US official who negotiated with Iran and is now with the International Institute for Strategic Studies (IISS) in London, told News Online: "Iran can sign the extra protocol and retain its weapons option.
"All it has to do is to allow the inspections and continue its programme. The IAEA has no powers to stop it. It can then give 90 days notice to leave the NTP."
Failure to comply
The IAEA has reported that Iran failed to comply with its obligations by not revealing until a very late stage that it was building a uranium enrichment plant and that it had imported uranium from China in 1991.
Iran is being urged to sign an additional protocol to the monitoring agreement which it, like other members of the Treaty developing nuclear power, already has with the IAEA.
This protocol would allow extra inspections (such as the sampling of air and soil) for suspected undeclared nuclear sites.
At issue is Iran's development at Natanz of a centrifuge for separating uranium 235 from the rest of the uranium ore.
Uranium 235 is needed to make the nuclear reaction. Only a tiny proportion (0.7%), it is the lightest part of the ore and sticks to the centre when the ore is spun in the centrifuge.
Experts say that by using this technology, which Iraq also tried to develop, Iran could eventually separate enough enriched uranium to make a nuclear device - 20 kilograms is needed as a minimum.
Mr Samore said: "Normally, you buy the enriched uranium from your supplier, which in Iran's case is Russia. Iran argues that it needs to do it itself for future expansion but there is no reasonable justification for this.
"It only has a nuclear reactor. Only a very few countries have enrichment plants."
Iran has said that it is developing a nuclear programme for peaceful purposes. Its former President Akbar Hashemi Rafsanjani said: "It is our right to benefit from nuclear power."
It attributes its failure to report its nuclear programme fully to differences of interpretation of the rules.
If Iran went for the nuclear bomb, it could trigger a confrontation with the United States and Israel.
The US National Security Adviser Condoleezza Rice has said that Iran might do "things that could lead to a nuclear weapons programme and that is unacceptable".
Israel showed in 1981, when it bombed Iraq's nuclear reactor, that it will act against what it sees as a fundamental threat.
There are fears that it is all getting too late to stop the spread of nuclear weapons, though there have been major successes such as the agreement to keep South America nuclear free.
"The genie is out of the bottle" according to the former Nato commander, retired US General Wesley Clark.