Romney sought to bolster his credentials to serve as commander-in-chief as new polls showed him back at the top of the Republican field and in a tight potential head-to-head matchup with Obama ahead of next year's election.
"God did not create this country to be a nation of followers. America is not destined to be one of several equally balanced global powers," Romney said, in the most important foreign policy speech of the Republican campaign so far.
"America must lead the world, or someone else will," he said, arguing that the globe would be more dangerous absent a prime role for Washington, Romney said in the speech, delivered on the 10th anniversary of the Afghan war.
"I will never, ever apologize for America," Romney said, surrounded by cadets at the Citadel, a military college in South Carolina.
Republicans have cast Obama's efforts to improve the image of the United States abroad as an "apology tour" and accuse the current administration of settling for a diminished US role in the world.
But Obama 2012 campaign spokesman Ben LaBolt said Romney's speech "proves once again that he is willing to say anything, regardless of the facts, to get elected."
"Governor Romney raised real questions about his capacity to lead this country and wage the fight against terrorism," LaBolt said, complaining Romney did not identify defeating Al-Qaeda as a goal.
"President Obama has degraded al Qaeda and dealt huge blows to its leadership, including eliminating Osama Bin Laden, ended the war in Iraq, promoted our security in Afghanistan while winding down our commitment in a responsible way and strengthened American leadership around the world."
Romney's speech appeared to be solidly in line with the notion of American exceptionalism, the idea that the United States is a uniquely special nation based on ideals of personal liberty.
Some Republican neoconservatives have interpreted the concept as a mission to promote freedom and democracy throughout the world.
Romney accused Obama of accepting American decline.
"An eloquently justified surrender of world leadership is still surrender," Romney said.
"This is very simple: If you do not want America to be the strongest nation on Earth, I am not your President.
"You have that President today."
Though potential presidents must convince voters that they are qualified to serve as commander-in-chief, the stagnant state of the US economy is already shaping up as the key issue in the 2012 race.
But the Obama team believes it has a trump card on security policy.
Romney's speech appeared to be an attempt to erode Obama's advantage and to portray himself as a prohibitive front-runner in the Republican race, and as the foreign policy heavyweight of the field.
It may also be seen as an effort to distinguish himself from rival Rick Perry, who was heavily criticized for a meandering answer on Pakistan in a recent campaign debate.
Romney promised immediate actions within the first 100 days of taking office, including:
-- An order to deploy a full, multi-layered national ballistic missile defense system -- a move likely to imperil US relations with Russia.
-- Romney would order the US navy to maintain regular patrols by aircraft carrier task groups in the Eastern Mediterranean and Persian Gulf to deter Iran.
-- The former Massachusetts governor also pledged to advance economic opportunity and democracy in Latin America and to leverage soft power to ensure the "Arab Spring does not fade into a long winter."
-- Romney also promised to make a decision about future US force levels in Afghanistan "free from politics" but remained unspecific on what he would do.
-- He also said he would renew US alliances which he said needed repairing after Obama, including the "special relationship" with Britain, the "Jewish State" of Israel and with Mexico, as it fights a drugs war.
Romney rolled out his plans after announcing a large foreign policy team which included a number of former Bush administration officials.
The Democratic National Committee said in a memo that the team dispelled any notion that Romney was a moderate.
"Discredited though they may be, the neoconservatives -- with all their bloody baggage -- are back."
