Iran's supreme leader says the US and its allies are influencing the UN nuclear watchdog agency's stance on Tehran's nuclear program.

Pakistan on Sunday junked as "rubbish" a report that elite US troops were ready to counter any move to hijack the country's nuclear arsenal and said it was "a figment of the imagination".

In a clear break from the past, a new prime minister has gone where none of his predecessors dared go: He has ordered a panel of ministry officials and academics to investigate the secret agreements.

Defence Minister A K Antony today said the threat of these weapons falling in wrong hands was an "area of serious concern" and its consequences would be "unimaginable".

"The US has no intention of seizing Pakistani nuclear weapons or material," State Department spokesman Ian Kelly told reporters at his daily news briefing.