The secret acquisition by Iran and Libya of nuclear centrifuge technology has revealed a gap in the policing of weapon development which needs closing, according to experts.
The attempt to prevent more countries from building the bomb is matched only by President George Bush's war on terror as the number one priority in US foreign policy, strongly supported by Britain.
There are concerns about the nature of Iran's nuclear programme
Recent revelations have demonstrated that the soft underbelly of the Nuclear Non-Proliferation Treaty - designed to allow countries to develop nuclear power but not a nuclear bomb - is a black market in the technology to build centrifuges.
These are used to spin uranium material and separate the parts needed to make a nuclear explosion.
Under the NPT, countries are allowed to enrich uranium to a level needed to fuel nuclear power stations, so long as this is under the control of the UN's nuclear agency, the International Atomic Energy Agency (IAEA).
Most countries simply buy the fuel from the small number of recognised supplier governments.
The problem occurs when a government secretly develops the ability to enrich uranium to the higher levels needed for a nuclear bomb.
Libya has admitted that it has been developing this process as part of a programme to develop a nuclear weapon. Iran has said that it needs enriched uranium only as a fuel for its nuclear power station.
In both cases, a finger is pointing at scientists in Pakistan as a possible source for the technology. The Pakistani government has started an inquiry.
Dr Gary Samore, of the International Institute for Strategic Studies in London, said: "Closing this loophole is a good idea but it will be difficult to amend the NPT. Instead we need informal agreements on a case by case basis."
In an editorial, the New York Times said that there should be formal restrictions: "Reactor fuel production should be limited to the few advanced countries that already have fully transparent nuclear technology industries. Other countries should have a guaranteed right to purchase all the reactor fuel they need."
According to Dr Samore one of the problems was that centrifuges could be manufactured in parts almost anywhere and put together later. "You can make them in bits and pieces."
In October a shipment of such components was intercepted heading to Libya. It is thought that the parts were made in Malaysia and that the ship was loaded in Dubai.
The interception shows that the Proliferation Security Initiative, an attempt by the United States and ten other western countries to monitor this traffic, is well underway.
But it is sometimes hard to identify the parts. During the build up to the war in Iraq there was much discussion about thousands of tubes which Iraq had ordered and whether they were for centrifuges or for rockets.
The attention being given to centrifuges is part of the wider push on the issue of non-proliferation.
Gaddafi decided it was worth admitting his intentions
According to Leonard Spector of the Monterey Institute's Center for Nonproliferation Studies in Washington, recent moves by North Korea, Iran and Libya are the result of pressure from US foreign policy.
North Korea has invited a party of private American experts in to examine one of its nuclear sites and has offered terms for the restarting of talks about a nuclear freeze.
"The assertive US position has concentrated minds in each country and they have calculated their interests," Mr Spector he said.
However, he did not think that it was all over.
"The shipment to Libya was found even as Libya was talking to the US and UK, and Iran's future intentions remain to be seen. There is also a view that North Korea has invited the US experts in order to show how advanced its work is and so strengthen its bargaining position."
And Mr Spector said that there were other worries on the horizon. "I am looking at Myanmar [Burma] which is trying to get a larger reactor from Russia and at Egypt which has always been incensed that Israel is not part of the NPT.
"We also have to watch Syria. It has a chemical weapons programme and missiles which can reach round the region. The US will want Syria to accept more stringent inspections by the IAEA over whatever nuclear reactors it builds.
"The counter proliferation action has picked up since the events of 9/11," he said. "But so have the dangers."