The cuts over the next five years come in addition to US$100 billion in internal savings already announced.

Those savings will be redirected to other defence programmes, but the new cuts slow growth in the overall budget.

But cuts to weapons programmes are certain to encounter fierce opposition from members of Congress.

Much of the roughly US$178 billion in defence cuts will come through reduced administrative costs, new organisational efficiencies, and slashed personnel costs, which the defence department called a "vigorous scrub of bureaucratic structures".

The Pentagon's budget is expected to be US$553 billion in 2012, reflecting roughly 3 percent growth. After that, growth would slow and would be essentially flat in 2015 and 2016, the Pentagon said.

Mr Gates said much of the savings would be achieved by eliminating more than 100 general and flag officer positions, more than 200 top civilian defence positions, by cancelling redundant programmes and through reduced administrative costs.

As much as US$100 billion in savings would not be sliced from the overall budget, Mr Gates said, but would be reinvested in shipbuilding, missile defence, intelligence, reconnaissance, healthcare for wounded soldiers, and other programmes.