KING: The use of American military fire power in Libya is igniting a long standing and passionate debate about presidential powers. President Obama sent this letter to Congress today saying the use of force was well within his rights as commander-in-chief. As a senator he took a different view arguing that unless the United States was facing an immediate threat, a president, any president should get approval from Congress before using force.

Some on Capitol Hill are making that case now, as well as questioning exactly what the president hopes to accomplish in Libya. Among them, Senator Richard Lugar of Indiana, the ranking Republican on the Senate Foreign Relations Committee and a leading GOP voice on foreign affairs for more than a quarter century.

Senator Lugar, let me just start with what I would hope would be a pretty simple question to answer. Do you understand clearly the mission in Libya? When will we have success?

SEN. RICHARD LUGAR (R-IN), FOREIGN RELATIONS COMMITTEE: No, I do not understand the mission because as far as I can tell in the United States there is no mission and there are no guidelines for success. That may will be true with our allies although conceivably they may have other missions in mind and simply trying to get Security Council clearance to proceed.

KING: Well when you ask the White House for clarification, what's the answer?

LUGAR: Well there is no answer. There simply is the thought that the president gave to congressional leaders on Friday that no boots on the ground, no aircraft over, and he said it is days not months. Now that's not an answer to any of these questions.

KING: Do you believe the United States is leading here or is the United States being dragged along by Europeans who might have a more muscular, more aggressive position than the president does?

LUGAR: It would not appear that we're leading. And the fact that President Sarkozy of France called a meeting of the heads of state and gave a major press conference, was sort of an announcement at least that activity was going to occur, and we clearly are in a very supportive role and apparently have decided to have a very limited role.

KING: Your comments, some of your comments about this were run by the chairman of the committee now, Senator John Kerry. And he said "Senator Lugar is a wise, wise, you know, counselor on these issues. But we're not policing Libya. We're engaged in a humanitarian initiative to prevent the slaughter of innocent people." Is that what we're engaged in, a humanitarian mission?

LUGAR: Well that's been one definition of why we sent the 110 tomahawk missiles there.

KING: Have you ever seen 110 tomahawk cruise missiles used in a humanitarian mission?

LUGAR: Only in a broader sense that it would knock out aircraft facilities. And therefore that if Moammar Gadhafi was going to use aircraft to bomb opposition people he would be denied that opportunity. But as it stands, as far as we can tell Moammar Gadhafi is not only alive, but is in control of Tripoli. Likewise, and a great number of cities, apparently the government still in control in other places, so-called rebels appear to be in control.

And all of the people seem to have guns and other armament and they're frequently firing at each other. People are being killed. So the question is how do you stop the killing, I suppose. And furthermore, after you do, who do we recognize? Do we recognize Gadhafi who is still there after all this time or do we take further action to depose him, literally to eliminate his regime? That is not at all clear. In fact, it's hardly been discussed as far as I can tell.

KING: And you don't seem to think that there is a solution, a clear at least political solution in the foreseeable future here?

LUGAR: I think there may be a vague hope that due to the fact that there appear to be allies including the United States of America involved, that Moammar Gadhafi would step aside, would leave with his sons and his people, that by and large then that would emerge a group of people to roughly characteristic of the rebels and the various dissident groups in the various cities, with whom we could (INAUDIBLE) have to sort of organize them so we have someone to deal with at that point. But absent there being a plan for Gadhafi to go, merely calling for him to go does not appear to have been impressive (INAUDIBLE).

KING: Do you consider what's happening now an act of war by the United States?

LUGAR: Yes, it is. The president has indicated he believes he's within his constitutional rights and very limited scope of what he has suggested namely support of other countries in this respect. But nevertheless American armed forces have been at work. We did fire the tomahawk missiles. We apparently offered background support to the aircraft of the French and the British. And in my judgment, if we're not on the edge of an act of war, we are close enough that the president really ought to have a debate in the Congress, ought to have, on behalf of the American people, a very clear definition of why American forces are going to be at risk, what the objectives are so we can claim success on the bases literally of having to find what we're about.

KING: How would you have handled the communications of this differently if at all? I believe it's the first time the United States has launched weapons into a foreign country when the president was overseas. Do you think how it has been explained both to the Congress and the American people could have and should have been handled differently?

LUGAR: Well of course it should be handled differently. I'm not going to criticize the president's trip to Brazil. I think it was very important that he finally make this trip to Brazil and other important South American, Latin American countries who feel overlooked and they are important to us. But I think at the same time it comes with the Congress in recess, the president out of the country, and the fact that the mission was not defined at all as far as I can tell to begin with in terms of its objectives and what we do next in any of the cases try to part from the relationship with everything else going on with governments under fire in the Middle East. So that does require concerted effort by the president and the Congress and the American people to come to grips with this and decide as a matter of fact what kind of sacrifices we're prepared to make over what period of time.

KING: Senator Richard Lugar is the ranking Republican on the Senate Foreign Relations Committee. Senator, thanks for your time today.

LUGAR: Thank you, John.