The US military will become "leaner" while maintaining superiority as it switches focus to the Asia-Pacific, US President Barack Obama has announced.
In a rare appearance at the Pentagon, he unveiled a far-reaching defence review under which thousands of troops are expected to be axed.
He said the tide of war was receding, and the US needed to renew its economic strength.
The Pentagon faces more than $450bn (£288bn) in cuts over the next decade.
"So yes, our military will be leaner," Mr Obama told reporters, "but the world must know - the United States is going to maintain our military superiority with armed forces that are agile, flexible and ready for the full range of contingencies and threats."
'Moment of transition'
No specific cuts to troop numbers or weapons programmes were announced on Thursday - those are to be presented as part of the federal budget next month.
But a 10-15% reduction to the US Army and Marine Corps is being considered over the next decade - amounting to tens of thousands of troops, Obama administration officials have told US media.
Mr Obama said during a speech in Australia in November that the Asia Pacific was now a top priority for the US, in what was seen as a challenge to the rising regional power of China.
Joined by Defence Secretary Leon Panetta, President Obama stressed that the defence budget would still grow, but at a slower pace.
He said the US was "turning the page on a decade of war" and faced a "moment of transition".
"Even as our troops continue to fight in Afghanistan, the tide of war is receding," he said.
President Obama added: "At the same time, we have to renew our economic strength here at home, which is the foundation of our strength around the world. That includes putting our fiscal house in order."
The president said the new strategy would end "long-term, nation-building with large military footprints", with the Pentagon instead pursuing a national security strategy based on "smaller conventional ground forces".
Mr Panetta said the review would make the US military "more agile, more flexible, ready to deploy quickly".
Ground forces would see a new mix of active and reserve components, while increasing capacity to mobilise quickly, he added.
Mr Panetta emphasised the military would retain its ability to confront more than one threat at a time, and would be more flexible and adaptable than in the past.
But he also warned that further reductions to the Pentagon budget, possible at the end of the year if Congress proceeds with steep across-the-board cuts, would undermine the military's ability to function at full capacity.
Mr Obama has been closely involved with shaping the blueprint, meeting high-ranking defence officials six times since September.
Source: BBC News - Obama unveils new strategy for 'leaner' US military