The report, due on Thursday, will recommend the UN Security Council slows the spread of weapons using an explicit pledge of "collective action" against any state or group that launches a nuclear attack - or even threatens such an attack on a non-nuclear weapon state.

Kofi Annan, UN secretary-general, last year established a panel of 16 veteran politicians and diplomats from around the world to identify the main threats facing mankind.

It identifies nuclear proliferation as a particular danger and it warns:

"The nuclear proliferation regime is at risk because of lack of compliance with existing commitments, a changing international security environment and radical advances in technology.

"We are approaching a point at which the erosion of the nuclear regime could become irreversible, and result in a cascade of proliferation."

In 1963, four states had nuclear arsenals. Today, eight are known and several others are suspected of developing them. Close to 60 operate or are building nuclear reactors, and at least 30 can build nuclear weapons at short notice. Terrorists are also believed to be seeking them.

To help prevent secret weapons programmes, the panel will also urge all countries to stop building enrichment or reprocessing facilities, until a global scheme can let the International Atomic Energy Agency guarantee the supply of fissile material to genuine "civil nuclear users".

The panel examined threats, including terrorism, disease, poverty and environmental degradation. But the risk of nuclear Armageddon may be the most pressing and has led to disagreement over how to tackle nuclear advances in the Middle East, Asia and Latin America.

To reduce demand, it argues, nuclear weapons states "must honour their commitments to move towards disarmament", and reaffirm promises not to use nuclear weapons against non-nuclear states. The Security Council pledge for "collective action" could help ease non-nuclear states' concerns.

All de facto nuclear states, including Israel, Pakistan and India (which are not named), should "pledge a commitment to non-proliferation and disarmament", ratify the comprehensive test-ban treaty and support talks on a fissile material cut-off treaty.

To reduce supply, the panel says the IAEA's additional protocol should become the standard, and urges a new system whereby peaceful nuclear technology users could be guaranteed fissile material - although the right to use nuclear energy for peaceful purposes "must be preserved".

In a possible bow to Washington, it also calls on "all states" to join the US-led Proliferation Security Initiative, with UN Security Council backing.