WASHINGTON — 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 an expansive rationale for intervention in civil conflicts such as the push under way to topple Libyan leader Moammar Gadhafi.

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 Gadhafi 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.”

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 in December 2009 on “just wars” when he accepted the Nobel Peace Prize.

Since he announced the start of operations in Libya, 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.

Brendan Buck, a spokesman for House Speaker John Boehner, R-Ohio, said Monday night that “it was helpful that the American people were able to hear from their commander in chief tonight. Unfortunately, Americans waited a long time to get few new answers.”

“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,” Buck said. “Nine days into this military intervention, Americans still have no answer to the fundamental question: What does success in Libya look like?”

Maine’s congressional delegation held to the positions that members outlined last week regarding Libya.

Republican Sen. Olympia Snowe, a member of the Senate Select Committee on Intelligence, said Obama “failed to answer the question of how our current involvement in Libya will end and how long it will take to get there.”

“The fact is that transferring this operation to NATO does not constitute an exit strategy, and ultimately means the United States is still shouldering much of the burden,” she said.

GOP Sen. Susan Collins, a member of the Senate Armed Services Committee, said Obama’s speech was “overdue.” Collins said in a written statement that she remains “troubled that the president did not seek congressional consent prior to ordering an aggressive military action in the absence of national emergency.”

Democratic 2nd District Rep. Mike Michaud said that he was glad Obama was limiting U.S. military involvement.

“But I remain concerned about the costs of these operations, the lack of consultation with Congress, and the precedent these recent actions in Libya set,” he said.

Democratic 1st District Rep. Chellie Pingree said Gadhafi is “a brutal dictator, and the international community was able to step in and put a stop to the humanitarian crisis he was creating. But I agree with the president that it’s important our involvement in Libya be short, and it was important for him to say that to the American people.”

Obama said early in the conflict that Gadhafi, 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 Gadhafi out of power.”

But a United Nations resolution, propelled by Arab League support, authorized military operations only to protect civilians, not to overthrow the government. Obama said he will “actively pursue” Gadhafi’s ouster “through non-military means,” namely financial sanctions designed to pressure Gadhafi from 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,” Obama 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 others, 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.”

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 was diminishing the United States’ moral leadership, whether in promoting democracy or intervening to prevent a humanitarian crisis.

– MaineToday Media Washington Bureau Chief Jonathan Riskind contributed to this report.