President Obama delivered a broad defense Monday of his decision to intervene in Libya and of his leadership style, arguing that the United States has a strategic interest in preventing the killing of civilians around the world and that it must do so in partnership with other nations.

Speaking at the National Defense University, Obama used his first televised address since military operations began in Libya nine days ago to outline a moral rationale for intervention in civil conflicts such as the push underway to topple Libyan leader Moammar Gaddafi.

Facing accusations that he has not explained the United States’ interest in Libya’s war, Obama said the nation had a responsibility to prevent a mass killing after Gaddafi pledged to carry out a brutal reprisal campaign against civilians in rebel-held territory. He emphasized that the mission was undertaken with the United States’ closest allies, and that command of the military operation will be transferred to NATO on Wednesday.

“To brush aside America’s responsibility as a leader and — more profoundly — our responsibilities to our fellow human beings under such circumstances would have been a betrayal of who we are,” Obama told an audience of mid-career military officers, who remained quiet during much of the 27-minute address. “Some nations may be able to turn a blind eye to atrocities in other countries. The United States of America is different.”

At the same time, Obama stressed the limits he placed on the operation, saying he acted only after securing broad international cooperation, kept out U.S. ground forces, and planned for a quick transfer of command to European allies.

Those guidelines could dictate how Obama approaches similar civil conflicts, including the other popular uprising now recasting much of the Middle East. In the case of Libya, he said that expanding the operation from protecting civilians to removing Gaddafi from power would fracture the coalition of European and Arab support, leaving the United States to pick up the cost.

“To be blunt, we went down that road in Iraq,” Obama said, referring to the 2003 U.S.-led invasion that was done without United Nations approval. “Regime change there took eight years, thousands of American and Iraqi lives, and nearly $1 trillion. That is not something we can afford to repeat in Libya.”

Obama has sought to link American values with his foreign policy priorities throughout his presidency, and the arguments he laid out in his address Monday echoed those he made on “just war” when he accepted the Nobel Peace Prize in December 2009.

Since he announced the start of operations in Libya with a low-profile audio message from Brazil, Obama has faced a host of questions, from a war-weary public and a confused Congress, over how long the administration intends to fight in Libya and to what end.

Conservatives have accused him of indecision and of diminishing American leadership in the world, while his own party has been divided over the value of opening a third military front in a Muslim nation. A recent Gallup poll showed that 47 percent of Americans favor military action in Libya, the lowest support recorded at the start of any recent war.

Those concerns remained after Monday’s address, at least among congressional Republicans.

Sen. John McCain (Ariz.) said he welcomed Obama’s “strong defense of our military action in Libya, and I appreciate that he explained why this intervention was both right and necessary in light of the unprecedented democratic awakening now sweeping the broader Middle East.”

But, McCain added, “if our goal in Libya is worth fighting for, and I believe it is, then the United States must remain strongly engaged to force Gaddafi to leave power.”

Brendan Buck, a spokesman for House Speaker John A. Boehner (Ohio), said: “Whether it’s the American resources that will be required, our standards and objectives for engaging the rebel opposition, or how this action is consistent with U.S. policy goals, the speech failed to provide Americans much clarity to our involvement in Libya.”

Obama said early in the conflict that Gaddafi, the erratic army colonel who took power in a coup 41 years ago, “must leave” after turning against civilians to put down the armed rebellion. He said Monday that “there is no question that Libya — and the world — will be better off with Gaddafi out of power.”

But a U.N. resolution, propelled by Arab League support, authorized military operations only to protect civilians, not to overthrow the government. Obama said he will “actively pursue” Gaddafi’s ouster “through non-military means,” namely financial sanctions designed to pressure Gaddafi to leave office or turn his inner circle against him.

Obama’s challenge Monday was to clearly spell out the U.S. interest in the war and define the limits of military involvement. He did so, in part, by criticizing the terms of the recent discussion, saying that “much of the debate in Washington has put forward a false choice” in Libya.

“It is true that America cannot use our military wherever repression occurs,” he said. “And given the costs and risks of intervention, we must always measure our interests against the need for action. But that cannot be an argument for never acting on behalf of what’s right.”

Obama focused the address tightly on the Libyan conflict and devoted only a small portion of it to the swift changes unsettling the broader Middle East and North Africa. Popular uprisings have swept from power a pair of autocrats long allied with the United States in Egypt and Tunisia, and protests threaten a handful of other leaders, from Syrian President Bashar al-Assad to King Hamad ibn Isa al-Khalifa of Bahrain.

But Obama said that, beyond the moral necessity of preventing a mass killing, a massacre in Libya would have put “enormous strains on the peaceful yet fragile transitions in Egypt and Tunisia.”

“The democratic impulses that are dawning across the region would be eclipsed by the darkest form of dictatorship, as repressive leaders concluded that violence is the best strategy to cling to power,” Obama said. “So while I will never minimize the costs involved in military action, I am convinced that a failure to act would have carried a far greater price for America.”

In the context of American military campaigns, the timing of Obama’s speech was unusual, coming more than a week after the United States began missile strikes in Libya.

By waiting, the president was able to put a largely positive gloss on the campaign. The debilitating effects of days of airstrikes by U.S., French and British forces are evident on the ground, as a lightly trained rebel force appears to be steadily retaking a string of strategic coastal towns from Gaddafi’s weakened military.

Obama was also able to announce the transfer of the U.S. command of Operation Odyssey Dawn, as the campaign is known, to NATO, saying that the United States will move into a support role that will include providing intelligence, logistical support, search-and-rescue missions, and jamming government communications. It will also involve humanitarian assistance.

“The United States has done what we said we would do,” he said. “That is not to say that our work is complete.”

Since the Libyan conflict began six weeks ago, Obama has been content to allow European allies to take the lead on the international response. He feared that a prominent American role would alarm many in the Middle East, where the United States is deeply unpopular because of the war in Iraq and its perceived historical bias toward Israel.

Many conservatives and some liberal interventionists, however, worried that Obama is diminishing the United States’ moral leadership, whether in promoting democracy or intervening to prevent a humanitarian crisis.

“Contrary to the claims of some, American leadership is not simply a matter of going it alone and bearing all the burden ourselves,” Obama said. “Real leadership creates the conditions and coalitions for others to step up as well.”