President Obama speaks about the conflict in Libya during an address at the National Defense University in Washington March 28. (LARRY DOWNING/REUTERS)

President Obama appears to have answered some of the questions about his decision to intervene in Libya’s civil conflict in his speech Monday evening, but concerns remain among critics about how long the United States will be engaged in a third war and whom precisely the administration is supporting.

Obama received mostly high marks for his address at the National Defense University, his first televised speech on Libya since he authorized military operations there 10 days ago. Most of the support came from members of his own party, who praised the president for explaining the moral and strategic rationale behind his decision.

In a statement largely representative of the Democratic response, Rep. James E. Clyburn (S.C.), the House assistant minority leader, said Obama “made clear . . . that he acted in America’s values and interest and effectively led a limited and international effort supported by the Libyan opposition and the Arab league to do what he said we would do — stop Moammar Gaddafi’s deadly advance on his own people.

“As a result,” Clyburn said, “thousands of lives have been saved.”

But Republicans, though saying they were glad that Obama had directly addressed the nation on his Libya policy, argued that the president remained ambiguous about the length of the American commitment and his preferred endgame.

Speaking to reporters Tuesday, House Majority Leader Eric Cantor (R-Va.) said, “I didn’t see victory defined” in Obama’s speech.

“The president has said in one instance that Gaddafi’s got to go and regime change is the goal. If that’s the case, what are the elements that we need to see come into play to make that happen? What about the rebels? Who is it that we’re going to see step into the vacuum if it were to be created by Gaddafi’s exiting?” Cantor said. “There’s all kinds of unanswered questions right now, and hopefully the White House can come and brief members and we can begin to get some clarity.”

Sen. John McCain (R-Ariz.) said Obama did not say explicitly that military operations would continue until Gaddafi’s ouster, something that McCain has said he supports.

“Ultimately, we need to be straight with the American people and with ourselves: We are not neutral in the conflict in Libya,” McCain said Tuesday on the Senate floor. “We want the opposition to succeed, and we want Gaddafi to leave power. These are just causes. And we must therefore provide the necessary and appropriate assistance to aid the opposition in their fight.

Obama said that expanding the military mission to include regime change would splinter the Arab and European coalition behind the effort, which he warned would leave the United States bearing the brunt of the costs.

The president indicated that although he wants Gaddafi gone, a longer-term strategy involving sanctions and the threat of a war crimes indictment was in place to achieve that.

Asked Tuesday whether his concerns were addressed in Obama’s speech, House Speaker John A. Boehner (R-Ohio) said, “Some of my questions were answered by the president, I think, but others were not.

“The fact that the plan appeared to be a humanitarian mission to stop the slaughter of innocent people in Libya is certainly something I think most of the Congress would support. But the second part of the plan is ‘We hope Gaddafi leaves.’ I just don’t think that that is a strategy,” Boehner said. “And when you listen to all of what’s going on and all the words, it really is about . . . hope. So if Gaddafi doesn’t leave, how long will NATO be there to enforce a no-fly zone? That’s a very troubling question.”

Until Monday night, Obama had been accused of beginning a war — America’s third military front in a Muslim nation — without fully informing the public of the U.S. interests at stake.

In his 27-minute address, Obama outlined a moral argument for the intervention, saying that allowing Gaddafi to carry out his threatened reprisals against civilians in rebel-held territory would have been “a betrayal of who we are.”

But he made clear that he acted only after securing broad international support, including from the Arab League, and with a plan to quickly turn over military command to NATO. That will happen Wednesday, he was able to announce, thanks in part to waiting as long as he did to deliver his first televised address on the issue.

How such guidelines will shape Obama’s response to future civil conflicts, especially those underway in the Middle East, is unclear. His senior advisers say the American public should not expect consistency in Obama’s policy toward popular uprisings and autocratic governments.

As deputy national security adviser Denis McDonough put it Monday to reporters at the White House, “We don’t get very hung up on this question of precedent.

“We don’t make decisions about questions like intervention based on consistency or precedent,” he said. “We make them on how we can best advance our interests in the region.”

Those instructions are designed, in part, to quiet voices within the Democratic Party that wonder why Obama has not done more to help the opposition in Ivory Coast now trying to push out incumbent leader Laurent Gbagbo, who has refused to leave office after losing a November presidential election.

Scores of civilians have been killed by forces loyal to Gbagbo, and hundreds of thousands have fled their homes. Obama has issued several statements condemning the Gbagbo government’s crackdown.

Practical questions also remain about the Libyan operation, including some being raised by Democrats.

Those revolve around Libya’s rebel opposition, which is seeking to topple Gaddafi after 41 years in power. Little is known about the movement, particularly at the rank-and-file level, and fears are rising that some among them may be Islamist extremists.

“I don’t want to equate success of the rebels with the success of the United States,” Rep. Robert E. Andrews (D-N.J.) told MSNBC. “I don’t know who these people are.”

Staff writer Felicia Sonmez contributed to this report.