US submarines currently rely on the Trident missile system
The Bush administration has selected the design for America's first new nuclear warhead in nearly two decades.
US officials say the warhead will not add to the country's nuclear arsenal, but will replace existing missiles.
Critics have complained it sends the wrong signal at a time when the White House is leading efforts to curb Iran and North Korea's nuclear ambitions.
The chosen design was developed in a Californian laboratory and is based on a warhead already tested in the 1980s.
The US Congress authorised design work on a new warhead in 2005 on the basis that there would not be any fresh missile tests.
No nuclear underground tests have been conducted since a ban in 1992.
The new warhead, due to be operational in five years' time, will be used to replace Trident missiles on submarines.
'No arms race'
Making the announcement, US officials said the plan was simply to replace older, less reliable warheads with a safer version.
"This is not about starting a new nuclear arms race," said Thomas P D'Agostino, acting head of the National Nuclear Security Administration (NNSA).
Scientists at the Lawrence Livermore National Laboratory would now continue work on the design, costing and development of the programme, he said.
However, says the BBC's Jamie Coomarasamy in Washington, at a moment when the White House is trying to stop North Korea and Iran developing their nuclear programmes, some see the decision to press ahead with a new US warhead as sending an unfortunate mixed message.
Democratic Senator Dianne Feinstein was among the critics in Congress.
"The minute you begin to put more sophisticated nuclear warheads on the existing fleet, you are essentially creating a new nuclear weapon. And it's just a matter of time before other nations do the same," the Associated Press quotes her as saying.
"This could serve to encourage the very proliferation we are trying to prevent."
Nuclear non-proliferation groups have also criticised the move, warning that it could lead to proliferation and saying there is no need to replace the US' Cold War-era stockpile.
The NNSA has said the destruction of ageing warheads will mean that in five years' time, the number held by the US will be at its lowest since the 1950s.