President Barack Obama unveiled a defense strategy Thursday that would expand the US military presence in Asia but shrink the overall size of the force as the Pentagon seeks to slash spending by nearly half a trillion dollars after a decade of war.

The strategy, if carried out, would significantly reshape the world's most powerful military following the buildup that was a key part of President George W. Bush's 'war on terrorism' in Iraq and Afghanistan.

Cyberwarfare and unmanned drones would continue to grow in  priority, as would countering attempts by China and Iran to block US power projection capabilities in areas like the South China Sea and the Strait of Hormuz.

But the size of the US Army and Marines Corps would shrink. So too might the US nuclear arsenal and the US military footprint in Europe.

Troop- and time-intensive counter-insurgency operations, a staple of US military strategy since the 2007 'surge' of extra troops to Iraq, would be far more limited.

Smaller, leaner

Panetta said the new strategy would mean the Pentagon would field a 'smaller and leaner' military force, but added that the exact number of personnel would not be determined until the Defense Department finishes its proposed 2013 budget in the coming weeks. 

Administration officials have said they expect Army and Marine Corp personnel levels to be reduced by 10 percent to 15 percent over the next decade as part of the reductions.

The Army's current strength is about 565,000 soldiers and there are 201,000 Marines, meaning an eventual loss of between 76,000 and 114,000 troops.

Panetta acknowledged the Pentagon's financial constraints would mean difficult choices and trade-offs that would require the US to take on 'some level of additional but acceptable risk in the budget plan we release next month.'

Critics charged that the cuts were driven by budget woes rather than US defense needs.

'The Pentagon is trying to put on a brave face that this is a pure strategy that has informed the 2013 defense budget,' said Mackenzie Eaglen, a national security expert at the conservative Heritage Foundation think tank.

'Everyone knows that the cart was before the horse on this and that Congress and the president picked a budget and this is a strategy to chase down those numbers,' she said.

'This is a classic resource-driven strategy document,' said Gordon Adams, an American University professor who worked on defense budgets in the Clinton administration White House.

'That's not a criticism, that's just a reality. It's inevitable. Strategy always wears a dollar sign,' he said.

Obama and Panetta insisted that the reverse was true and that strategy would inform the spending decisions. But they did not divulge details of spending and cuts, which will be released as part of Obama's upcoming federal budget for fiscal year 2013.

The president emphasized that even after enactment of the $487 billion in reductions over 10 years that was agreed with Congress in August, the defense budget would still be larger than it was toward the end of Bush's administration.

'Over the past 10 years, since 9/11, our defense budget grew at an extraordinary pace,' Obama said. 'Over the next 10 years, the growth in the defense budget will slow but the fact of the matter is this - it will still grow because we have global responsibilities that demand our leadership.'

The shift in focus to Asia comes amid increasing concern at the Pentagon over China's strategic goals as it begins to field a new generation of weapons that American officials fear are designed to prevent US naval and air forces from projecting power into the Far East.

The new strategy also calls for increased investment in cyber capabilities and suggests the US may be able to shrink its nuclear arsenal further without jeopardizing security, a statement welcomed by arms control groups and some lawmakers.

One war, two wars

The strategy says the US should maintain a force that can win one major war while still being able to deter an aggressor in a second conflict. In the past the Pentagon has tried to field a force that could fight and win two major wars at once.

Panetta played down the differences, saying the earlier strategy dealt with large conflicts of the past while the current strategy was considering the conflicts the US is likely to face in the 21st century.

'Make no mistake - we will have the capability to confront and defeat more than one adversary at a time,' he said.

But Representative Mike Coffman, a member of the House Armed Services Committee, expressed alarm over the shift in US posture, saying, 'I believe we can make cuts that don't reduce capability,' a concern that was echoed by Lieberman.

The strategy also highlights the US interest in maintaining stability in the Middle East while responding to the aspirations of the people as expressed in the 'Arab spring' last year. It also says the US will continue working to halt nuclear programs in Iran and North Korea. – Reuters