In his first address to military graduates, Mr Obama also pledged to invest in the men and women who defend America's liberty, not just in the weapons they take with them into battle.

'I will only send you into harm's way when it is absolutely necessary, and with the strategy, the well-defined goals, the equipment and the support that you need to get the job done,' the president told more than 1,000 graduates during a sun-splashed ceremony at Navy-Marine Corps Memorial Stadium on the shores of the Chesapeake Bay.

Mr Obama praised the role of Navy Seals in freeing a US sea captain by killing his Somali pirate captors last month.

'The extraordinary precision and professionalism displayed that day was made possible, in no small measure, by the training, the discipline and the leadership skills that so many of those officers learned at the United States Naval Academy,' Mr Obama said.

The president said he has halted reductions in the Navy, is building up the Marine Corps and investing in the hardware - combat ships, submarines and fighter aircraft - they will need to do their jobs. He also promised higher pay, enhanced child care and improved support and other benefits.

'In short, we will maintain America's military dominance and keep you the finest fighting force the world has ever seen,' Mr Obama said, as more than 30,000 watched from the stands.

The ceremony included the son of Mr Obama's presidential rival, Sen John McCain, who was among the proud parents.

Mr Obama did not recognise Mr McCain in his speech.

But he did so before leaving the White House, praising the senator as he signed into law legislation giving the Pentagon new power to curtail wasteful defence spending. -- AP