The Obama administration is leaving little doubt that it has already decided to attack Syria in response to the chemical weapons allegedly used by the Assad regime.

The operation's targets are still unclear as is the duration, but the Americans, along with their British and French allies, have no intention- for now at least- of deploying ground troops in Syria.

Even with air-strikes there are different levels of involvement. So far the Americans do not seem interested in conducting an operation that will directly topple Bashar Assad, only in proving to Syria and to the world that they will not tolerate any use of weapons of mass destruction. But a one-off attack can quickly evolve into a rolling operation.

Here are a few possible scenarios:

Striking symbolic targets

The Americans will probably not hit the presidential palace or civilian offices of the regime. Central military bases and command and control centers are the most likely to be targeted, especially those associated with the Fourth Division and the Republican Guard, the forces most loyal to the regime, which are suspected of having been involved in the use of chemical weapons. Bombing these targets may not cause major damage to the regime but they will be highly symbolic.

These targets will probably be bombed using Tomahawk cruise missiles launched from U.S. Navy destroyers and submarines and probably also a British submarine, all currently based in the eastern end of the Mediterranean. If the Americans plan to bomb a wider area (such as a large military compound) and not just pinpoint targets, they are likely also to use the B-2 stealth bomber that carries a much larger load of explosives than a cruise missile and will easily be able to evade the air-defense systems around Damascus.

Elimination of chemical weapons stockpiles

Attacking storage facilities of chemical weapons with large conventional bombs could cause serious environmental damage and many casualties from a cloud of poisonous gas created by the explosion. For that reason mainly, the Americans will probably not try to take out the chemical weapons anytime soon. But if they decide to do so, the U.S. military has special bombs which disperse thousands of small metal rods and darts over a wide area and are supposed to puncture and destroy chemical containers and bombs and which spray the area with chemicals that can neutralize the poisonous gases without causing environmental damage.

The downside of these bombs is that they need to be dropped relatively close to the target exposing the aircraft to Syrian air-defense and necessitating a larger operation to neutralize anti-aircraft batteries.

Despite the reports on fighter planes landing at the British air-base in Cyprus, there are nowhere enough bombers and electronic-warfare aircraft currently near Syria to carry out such a complex and lengthy operation and it will take a buildup of at least a few weeks to prepare for for it.

Destroying Syria's air-force

According to most assessments, the Syrian Air Force currently has less than a hundred fixed-wing aircraft capable of flight condition and about fifty helicopters. But this is still a significant advantage over the rebels who have no air-power. If the Obama administration wished to intervene on the side of the rebels and greatly improve their situation in a way that wouldn't endanger American personnel and not take the risk of advanced weapons falling in the hands of Jihadists, they could deny the Assad regime its air-power by bombing the six air-bases still in use, destroying most of its remaining aircraft on the ground.

Such a strike could be carried out using a combination of cruise missiles launched from the Mediterranean and stand-off missiles from fighter jets flying well outside the range of Syria's anti-aircraft missiles. The planes could take off from an aircraft carrier or from a NATO base in Europe.

Constant aerial presence

The civil war in Libya was won two years ago only after NATO members began keeping up a nearly constant presence over the areas of fighting, attacking Libyan army positions according to coordinates they received from observers on the ground (special-forces operatives or English-speaking rebels who had been specially trained). Such a presence over Syria will be possible only once Syrian air-defense has been destroyed and of course will happen only if the administration decides further down the road to actively bring about Assad's downfall.

It will need an aircraft carrier stationed in the eastern Mediterranean (the U.S. Navy currently has two carriers southeast of the Suez Canal but neither has begun to sail north) and it will need to deploy large numbers of fighter jets and support aircraft from bases in nearby countries, mainly Greece, Turkey and Cyprus. In addition, squadrons of aerial tankers will have to constantly fly over the Mediterranean to refuel the jets.

Another method for keeping up air-support for the rebels would be operating armed drones over Syria, as the U.S. does over Pakistan and Yemen. These drones do not have aerial refueling capabilities and would have to operate from a base near Syria's borders, probably Jordan or Turkey.