"When the US says we're going to build new nuclear weapons, and we go to Iran and say you cant have nuclear weapons at all, that is just going to be one more reason why the folks in Iran ... are going to dismiss it as US hypocrisy," John Pike, director of GlobalSecurity.org, a security information wesbite, told Al Jazeera.

The government chose a design from a laboratory in California for the project, the department of energy's National Nuclear Security Administration (NNSA) said in a statement on Friday.

 

Technological advancement

 

The programme, named Reliable Replacement Warhead, will enter a new phase of development and after congressional approval the new warheads will be produced under the direction of the US navy, officials said.

 

"RRW will take advantage of today's science to ensure long-term confidence in the future stockpile" of nuclear warheads, the Washington Post newspaper reported Thomas D'Agostino, the NNSA's acting administrator, as saying.

  

The new design is similar to that of bombs used in the most recent underground tests, which increases the likelihood it will not have to undergo new testing, NNSA said.

  

The NNSA said the new nuclear warheads would not increase the US army's stockpile, but will replace existing warheads which on average are more than 20 years old and at risk of becoming dangerous.

D'Agostino said designers will work with the navy over the next 10 months to devised a production plan and calculate costs.

The NNSA's 2008 budget includes $88m for the RRW, though congress could limit the funding and slow the programme, the Washington Post reported.

The NNSA has long said that one goal of the RRW is to "render unauthorised use of weapons impossible".

The new design includes a device which locks a weapon's nuclear element so it cannot be used if it fell into enemy hands.