Silicon Valley: The United States administration has taken a major step towards developing a new generation of nuclear weapons, with a Senate panel clearing the way for lifting a 10-year ban on researching small atomic bombs and funding more study on a nuclear "bunker-buster" bomb.

The annual Defence Authorisation Bill, approved by the Senate Armed Services Committee on May 9, will also increase funding for a nuclear weapons site in Nevada to enable the Pentagon, if necessary, to resume faster, the weapons testing it suspended 11 years ago, the 'Los Angeles Times' reported from Washington on May 10.

The administration had been moving to develop options with nuclear weapons to enable it to better deal with emerging threats, such as the deeply buried bunkers where potential adversaries may conceal banned weapons and missiles, the paper said.

The United States has not designed any new nuclear weapons since the end of the cold war, as it has worked with Russia to scale back strategic nuclear arsenals.

However, since President George W Bush came into office, the administration has been formulating a new policy and is now beginning to carry out the changes.

This new tactic, the paper said, had alarmed arms control advocates, who fear that the availability of smaller bombs that promise less secondary damage would encourage nations to use weapons that have been nearly unthinkable for half a century.

They worry that expansion of the US nuclear arsenal would encourage more countries to build weapons and weaken already fragile international non-proliferation efforts.

"We're moving away from more than five decades of efforts to de-legitimise the use of nuclear weapons," Senator Jack Reed a member of the Senate Armed Services Committee, said.

The Bill, to be considered on the floor of the Senate and House this month, provides $ 15.5 million in funding for research on a large hydrogen bunker-buster bomb called the Robust Nuclear Earth Penetrator.

This bomb is a re-designed version of an existing nuclear weapon to make it burrow deeply into the earth better.

Unlike the proposed low-yield bombs, which have an explosive force of no more than five kilo tonnes, this weapon would have yields in the range of tens of kilo tonnes, to a mega tonne, making it at least six times more powerful than the bomb that was dropped on Hiroshima.

The Bill sets aside $ six million for advanced research on nuclear weapons and also seeks $ 25 million in improvements to the Nevada nuclear weapons test site and US nuclear labs because US officials fear some of the nuclear infrastructure has become unreliable since former President Bill Clinton declared a voluntary test moratorium.

PTI