More than 130 experts and non-governmental organisations from 23 countries have criticised the Indo-US nuclear deal, saying its proposal to exempt India from the long-standing global nuclear trade standards "would damage the already fragile nuclear nonproliferation system and set back efforts to achieve universal nuclear disarmament".

In a letter to more than four-dozen governments this week, they called upon the governments to play an active role in supporting measures that would ensure this controversial proposal does not: further undermine the nuclear safeguards system and efforts to prevent the proliferation of technologies that may be used to produce nuclear bomb material, or in any way contribute to the expansion of India's nuclear arsenal.

The letter -- described as an "international appeal"-- urges the governments to consider additional conditions and restrictions on nuclear trade with India.

Among other recommendations, it urges ''to actively oppose any arrangement that would give India any special safeguards exemptions or would in any way be inconsistent with the principle of permanent safeguards over all nuclear materials and facilities".

Among the signatories to the 'international appeal', include former UN undersecretary General for Disarmament Affairs and President of the 1995 Nuclear Nonproliferation Treaty Review and Extension Conference Jayantha Dhanapala, mayors of Hiroshima and Nagasaki, the Tokyo-based Citizens' Nuclear Information Center and the Washington-based Arms Control Association.

The appeal insists that NSG states should under no circumstances allow for the transfer to India of plutonium reprocessing, uranium enrichment, or heavy water production technology, which may be replicated and used to help produce nuclear bomb material.

In the coming weeks, the 35-member International Atomic Energy Agency (IAEA) Board of Governors and the 45-member Nuclear Suppliers Group (NSG) will likely take up the issue.