Calling for a new “American century,” Republican presidential candidate Mitt Romney laid out a muscular agenda for promoting U.S. interests abroad, saying here Friday that he would expand naval and missile defense systems and repair relationships with Israel, Mexico and other U.S. allies.

Romney said he immediately would review U.S. troop commitments in Afghanistan and would make a decision “free of politics” by surveying generals in the field, but he offered no detailed plan for withdrawing from the decade-long war there. The former Massachusetts governor sharply condemned the isolationist policies pushed by some Democrats and, increasingly, leaders of his own party.

Delivering his first major foreign policy address of his 2012 campaign, Romney said he would try to work in concert with multilateral institutions such as the United Nations. But too often, he said, they become “forums for the tantrums of tyrants.” Romney said his administration would act alone whenever necessary to protect national security interests.

“This century must be an American century,” Romney said. “In an American century, America leads the free world and the free world leads the entire world.

“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. America must lead the world, or someone else will. Without American leadership, without clarity of American purpose and resolve, the world becomes a far more dangerous place, and liberty and prosperity would surely be among the first casualties.”

Speaking against the backdrop of about 200 uniformed cadets here at the Citadel, a South Carolina military college that has sent more than 1,400 alumni to the wars in Iraq and Afghanistan, Romney assailed President Obama’s foreign policies. In his 23-minute speech, Romney said Obama’s agenda is undermining the nation’s economy, defense and “the enduring strength of our values.”

“This is America’s moment,” Romney said. “We should embrace the challenge, not shrink from it, not crawl into an isolationist shell, not wave the white flag of surrender, nor give in to those who assert that America’s time has passed. That’s utter nonsense.

“An eloquently justified surrender of world leadership is still surrender. I will not surrender America’s role in the world. This is very simple: If you do not want America to be the strongest nation on Earth, I’m not your president. You have that president today.”

Romney said he would “apply the full spectrum of hard and soft power to influence events before they erupt into conflict,” adding that the nation must maintain military supremacy.

“It is far too easy for a president to jump from crisis to crisis, dealing with one hot spot after another,” Romney said. “But to do so is to be shaped by events rather than to shape events. To avoid this paralyzing seduction of action rather than progress, a president must have a broad vision of the world coupled with clarity of purpose.”

Romney pledged to take eight specific actions in the first 100 days of his administration, including increasing naval shipbuilding from nine per year to 15 per year; strengthening alliances with the United Kingdom, Israel and Mexico; regularly keeping aircraft carrier groups in the eastern Mediterranean and the Persian Gulf region as a deterrent against Iran; reversing Obama-era budget cuts to national missile defense; organizing and streamlining diplomatic and assistance efforts in the Middle East; launching a public-diplomacy and trade campaign in Latin America; reviewing the military and assistance presence in Afghanistan; and developing a unified national cybersecurity strategy.

The aggressive and hawkish foreign policy agenda Romney presented marks a return to the prevailing GOP posture during the Bush years, even as the tea party and libertarian wings of his party increasingly advocate a more isolationist approach. With his forceful speech, Romney is trying to establish his foreign policy bonafides. Romney spent most of his career in the business world and has far less experience abroad than some of his rivals, in particular former ambassador to China Jon Huntsman Jr., who will deliver his own foreign policy address next week in New Hampshire.

Romney spoke of growing up during the Cold War — “a classic baby boomer,” he said — and practicing “duck and cover” drills in school. Today, he said, “our world is far more chaotic.

“We still face grave threats, but they come not from one country, or one group, or one ideology,” Romney said, adding later: “There is no one approach to these challenges. There is no wall that the next president can demand to be torn down. But there is one unifying thread that connects each of these threats: When America is strong, the world is safer.”

Romney said that while the World War II Greatest Generation’s “light fades, we must seize the torch they carried so gallantly at such great sacrifice. It is an eternal torch of decency, freedom and hope. It is not America’s torch alone. But it’s America’s duty and honor to hold it high enough that all the world can see its light.”

Romney hammered his contrast with Obama, taking not-so-subtle digs at the president. “I will never, ever apologize for America,” Romney said, drawing sustained applause from his supporters here.

But in a conference call with reporters, his advisers said there were some differences between Romney’s foreign affairs agenda and President George W. Bush’s policies. Asked where Romney’s plan differs from Bush’s record, they said Romney would focus more on Latin America with a plan for a public-diplomacy and trade promotion campaign there.

“Neither the Bush administration nor the Obama administration really focused on Latin America,” said one adviser, who requested anonymity because he was not authorized to speak publicly about Romney’s plan. “I think President Bush, in part because of Iraq and Afghanistan, wasn’t looking to our neighbors in our hemisphere.”

Democrats rebutted Romney’s statements, saying Obama has kept the nation safe while rooting out terrorist leaders, most prominently this spring’s killing of Osama bin Laden.

Following the speech, Obama campaign spokesman Ben LaBolt said in a statement, “Governor Romney raised real questions about his capacity to lead this country and wage the fight against terrorism. He didn’t outline a strategy to strengthen America’s security and promote our interests and didn’t even 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.”

Priorities USA Action, a Democratic political action committee started by former Obama aides, released a tough Web video featuring footage of Sen. John McCain (R-Ariz.), in a 2008 presidential debate with Romney, questioning whether Romney has the “experience and judgement to lead this country in the war against radical Islamic extremism.”

Then, the narrator says: “Mitt Romney may have no experience fighting terror, but he does have some experience with foreign countries — sending our jobs to them.”