President Barack Obama unveiled a strategy on Thursday for a leaner US military focused on countering China's rising power while signaling a shift away from large ground wars against insurgents.

The plan calls for preparing for possible challenges from Iran and China with air and naval power while downplaying any future massive counter-insurgency campaigns like those in Iraq and Afghanistan.

The "defense strategic review" sets out an approach for the US military in an era of austerity, as Obama's administration prepares for $487 billion in defense cuts over the next 10 years.

But Obama, anticipating attacks from his Republican rivals in an election year, said defense reductions would be limited and not come at the expense of America's military might.

"So yes, our military will be leaner, 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," Obama told reporters at an unusual appearance at the Pentagon.

White House officials stressed Obama was deeply involved in the strategy review and sought to portray the president as taking a careful approach to defense spending informed by the advice of commanders.

Saying the country was "turning a page" on a decade of war, Obama said the new strategy would increasingly focus on Asia, where commanders worry about China's growing military punch.

"We'll be strengthening our presence in the Asia Pacific, and budget reductions will not come at the expense of this critical region," he said.

Defense Secretary Leon Panetta, appearing with Obama along with top officers, said the strategy envisages a "smaller and leaner" force that will expand the military's role in Asia while maintaining a strong military presence in the Middle East.

According to the eight-page strategy document, the American military will work with allies in the Middle East to ensure security in the Gulf and counter Iran's "destabilizing policies."

However, counter-insurgency operations, like those in Iraq and Afghanistan, receive a lower priority under the new plan, enabling the administration to scale back ground forces.

Panetta said "with the end of US military commitments in Iraq, and the drawdown already under way in Afghanistan, the Army and Marine Corps will no longer need to be sized to support the large scale, long-term stability operations that dominated military priorities and force generation over the past decade."

The review reinforces what defense officials have already signaled -- that funds will flow to aircraft and ships while the US Army and Marine Corps will be downsized after having expanded during a decade of ground warfare.

Washington's focus on Asia is fueled by concerns over China's growing navy and arsenal of anti-ship missiles that could jeopardize America's military power in the Pacific and access to the mineral-rich South China Sea.

"This region is growing in importance to the future of the United States economy and our national security. This means, for instance, improving capabilities that maintain our military's technological edge and freedom of action," Panetta said.

In keeping with plans for a smaller force, the strategy discards the doctrine that the American military must be prepared to fight two wars at the same time, an idea long debated inside the Pentagon.

Instead, the United States would be ready to fight one war while waging a holding action elsewhere to stave off a second threat.

The strategy review suggests reducing the nuclear arsenal without saying how, amid calls from some lawmakers reduce the number of nuclear-armed submarines.

The review also hints at reducing the military's footprint in Europe but offered no details, saying "our posture in Europe must also evolve."

The new strategy comes ahead of the proposed defense budget for 2013 due to be released in coming weeks, which is expected to call for delays in some weapons programs, including the troubled F-35 fighter jet.

Despite talk of belt-tightening, the annual defense budget is at nearly $700 billion and Obama said that future military spending will still remain high, dwarfing that of other nations.

The next budget will be "larger than roughly the next 10 countries combined."