United Nations: Three of the five declared nuclear weapon states, Britain, France and Russia, joined 15 other countries on September 14 in calling on key nations to ratify the 1996 Comprehensive Test Ban Treaty (CTBT).

They appealed to 13 countries, including the United States, China, India, Pakistan, Israel and Iran, whose ratification is essential for the treaty to come into force.

In a statement signed by their foreign ministers, 18 countries said the early entry into force of the CTBT was "central to nuclear disarmament and non-proliferation objectives".

The ministers were in New York for the 57th UN General Assembly.

Their statement echoed speakers who told the Assembly that the risk of terrorists getting their hands on nuclear weapons was one of the greatest threats to world peace and security today.

Those speakers included US President George W Bush, whose country has the largest nuclear arsenal but has refused to ratify the CTBT.

"We call upon all states that have not yet signed and ratified the CTBT to sign and ratify the treaty as soon as possible," the statement said.

All international treaties need the ratification of a certain number of states in order to take effect. Uniquely, in the case of the CTBT, the 44 countries are named, they are those known to possess or thought to have the capability of producing, nuclear weapons.

So far, only 31 of the 44 have ratified. Ten of the others have signed but not ratified, while India, Pakistan and North Korea have not even signed.

Alluding to the underground tests carried out by India and Pakistan in May 1998, the statement said, "International tensions have developed since the CTBT was negotiated which make entry into force of the treaty, even more urgent today."

The statement called on all states to continue a moratorium on nuclear testing, but said a voluntary ban on tests was no substitute for entry into force of the CTBT.

It also appealed to all states that have signed the treaty to provide the finances necessary to build and operate the CTBT's complex worldwide verification mechanism.

Much of the system is already in place, and when complete, it will consist of 321 monitoring stations and 16 laboratories based in 89 countries, some of them tiny islands in the Atlantic, Indian and Pacific oceans.

"The verification system will be unprecedented in its global reach," the statement said. It added that the system would gather scientific data and act as a vehicle for technological transfers from rich to developing countries.

The statement was signed by Australia, Britain, Canada Chile, France, Hungary. Japan, Jordan, the Netherlands, New Zealand, Nigeria, Peru, the Philippines, Russia, South Africa, South Korea, Sweden and Turkey.