While taking action in Syria will not be simple or cheap, it will ultimately be less costly than losing control of chemical weapons or letting Jordan and other neighbors be destabilized.

Israel has once again demonstrated that when it sets a red line with its neighbors, it means it. Having declared that they will prevent qualitatively new arms from being transferred from Syria to Hezbollah, the Israelis, without openly admitting it, acted to enforce this threshold.

Two points stand out: First, Israel has been able to do this with little regard for Syrian air defenses. Second, its targets and objectives have been very clear and discrete. Israel is not intervening on the side of the Syrian opposition. Israel's leaders seem to be banking on Assad's and Hezbollah's preoccupation with the Syrian regime's fight for survival -- and their understanding that they can ill afford also to engage Israel. Iran, too, having invested so much in Assad's survival, may feel that any responses should be indirect, particularly with a country that acts on its red lines.

Does Israel's action offer a lesson for the Obama Administration as it wrestles with how to respond to the Syrian use of chemical weapons? Perhaps, but they should not be overdrawn. First, the Israeli use of stand-off missiles has allowed them to strike without going into Syrian air space. Certainly, we could learn from this, but the key lesson is to have discrete, meaningful targets to hit. Can one impose a no-fly zone in this fashion? It would surely require either a significant build-up of tactical air forces in nearby countries (e.g., Turkey and Jordan) -- or the movement of two carrier battle groups into the Eastern Mediterranean to sustain an ongoing operation. Such an option could be adopted, but it is not one that draws from the Israeli example except insofar as it would rely on stand-off air-to-air and air-to-ground missiles.

An option that would be more consistent with the Israeli model would be to make clear that we will target discrete Syrian forces or units that employ chemical weapons -- or more ambitiously, we could target those Syrian air bases that are used to attack cities and villages with conventional bombs.

But this gets to the larger issue. The Israelis are acting on their red line and President Obama will have to act on his. As President Obama likes to say, he does not bluff. The real question for the Administration is not whether we must respond to the crossing of the red line. We must. Rather the question is this: Are we going to have a one-off kind of action to show there is a price for the Syrian breach of our red line, or are we going to use the Syrian game-changer to change the game in Syria?

The answer is not self-evident because, at this point, no one can guarantee a good outcome in Syria. Then-Secretary of State Warren Christopher once referred to the conflict in Bosnia as the "problem from hell." Unfortunately, Syria today makes the Bosnia conflict appear simple by comparison. The opposition remains fragmented, with Islamist groups having gained the upper hand in no small part because they have received far more arms and money than the more secular forces. The minorities in Syria may have little love for Bashar Assad, but fear what Syria's Sunni majority -- and the Islamist groups -- may do to them once he is gone. The numbers killed grow by the day and create massive numbers of Syrians fleeing their homes; internally, as many as 3 to 4 million people are displaced within the country and externally 1.4 million people are now formally registered as refugees -- a number that actually understates those who are now refugees in Jordan, Turkey, Lebanon, and Iraq.

In Syria, we are witnessing a humanitarian catastrophe that also confronts us with a strategic threat. We can ill afford to see chemical weapons fall into hands of Al Qaeda-type groups or for the war to spill-over into neighboring states -- and compel an American intervention in worse circumstances.

The problem is not that we lack options in Syria, but that we don't know whether any of our options can produce a minimally tolerable outcome. Unfortunately, at this point, it may already be too late to influence the realities on the ground given the scale of the killing, the sectarian divide, the loss of salvageable central authority, the fragmentation of the country, and the impossibility of fostering a political transition so long as Assad is there. The current U.S.-Russian initiative to bring together representatives of the Syrian regime with the opposition may be worth a try, but unless something changes -- and Russian dissociation from Assad might be a political game-changer -- it is hard to see negotiations progressing.

If we accept that all this is true, it may leave us little choice but to pursue a containment strategy to prevent the war from spreading and de-stabilizing Syria's neighbors. But before we opt for containment, we should think hard about whether it is possible to offer protection to the Syria public with at least a limited no-fly zone or whether our provision of lethal assistance might yet alter the balance of power within the opposition and between it and the regime. Our readiness to act on either might provide leverage on the Russians to end their support for Assad.

With regard to providing lethal assistance, it could be our response to Syria's breach of our red line. Alternatively, we could decide to use it to try to influence the landscape in Syria. If we are serious about this larger objective, we will have to convince others that we are now determined to break the stalemate in Syria even as we think about the "day after" Assad is gone. That will require us to lead an effort to support those in the opposition that are committed to a non-sectarian and inclusive Syria and it will mean producing significant arms, money, training, and intensive coordination between our allies, and especially the Saudis and the Qataris, to ensure that weapons go only through one channel.

For this to happen, the President would have to gain the acceptance of other leaders and then designate a senior official whose only job is to oversee this effort. For the first time, we would have to ensure that there is one address for the opposition and one mechanism for those helping it -- and that will take a determined and unrelenting effort to coordinate all moves, a clearing house for the movement of money and arms, and probably a CIA presence on the ground to ensure that those we are supporting -- and not others -- are actually getting the material support and using it as intended.

If we judge this to be too difficult, it is better to focus on containment and building buffers in and around Syria with our allies. While that may not be simple or cheap, it will ultimately be less costly than losing control of chemical weapons or letting countries like Jordan be de-stabilized.

Ambassador Dennis Ross is counselor at The Washington Institute.