UNITED NATIONS, April 27: The United States said on Tuesday that countries developing or acquiring nuclear weapons should forfeit the right to nuclear technology for peaceful uses.

The comments, in a speech to a United Nations conference by Undersecretary of State John Bolton, reflect an increasingly aggressive US effort to hold states like Iran accountable for their secret nuclear arms programmes, US officials said.

"The central bargain of the NPT (nuclear Non-Proliferation Treaty) is that if non-nuclear weapons states renounce the pursuit of nuclear weapons, they may gain assistance in developing civilian nuclear power," Mr Bolton said.

"If a state party seeks to acquire nuclear weapons and thus fails to conform with Article II (of the treaty), then under the treaty that party forfeits the right to develop peaceful nuclear energy," he told a UN conference reviewing progress on the 34-year-old NPT.

Although the United States has repeatedly accused Iran of developing a clandestine nuclear weapons programme, officials said this was the first time Washington had explicitly asserted that this behaviour should be interpreted under the NPT as grounds for halting peaceful nuclear cooperation with Tehran.

US officials hope it will give countries like Russia, which is building a major nuclear reactor for Iran, more incentive to halt that cooperation. Mr Bolton warned of a 'crisis of NPT compliance' and said if treaty provisions were ignored, the confidence in the security benefits derived from the NPT would erode.

"Enforcement is critical. We must increase the costs and reduce the benefits to violators," he said.

STRAINS IN TREATY: The NPT, signed by 189 nations, is under severe strain. US officials say Iran and North Korea have used the treaty as a cover to pursue nuclear capabilities.