POSSIBLE MILITARY OPTIONS FOR THE US IN SYRIA

1.Strategic Airstrikes

The US could seek to carry out punitive airstrikes against Syrian military assets or even its leadership. But a major obstacle lies in the way: Russian air defense systems within Syria effectively give Moscow control of the airspace over much of Syria. Since it is highly unlikely that Russia would allow US strikes against its ally, the US would have to use stealth aircraft to try to evade detection by the Russian air defenses.That would be a very expensive option with a limited number of aircraft available. If strikes went ahead, potential targets could include military depots, storage sites or Syrian air defenses. A complicating factor is that Russian specialists could be embedded with Syrian forces. The Trump administration would have to weigh whether it is willing to risk any Russian casualties, given the potential to escalate hostilities. Other options could include identifying and destroying the aircraft or artillery involved in launching the chemical weapons, or launching an air attack on the Syrian and allied ground forces advancing on opposition-controlled areas.

2. Cruise missiles

Another option is the launch of cruise missiles from US destroyers deployed in the Mediterranean. Deploying cruise missiles against command and control targets in Syria, as well as chemical weapon launchers. The problem is that cruise missiles are less useful for hitting moving targets and carry a greater risk that they will go astray and kill civilians.

3. 'No-fly' zone

There could be talk of the US imposing "no-fly" zones on the Syrian air forces, but this would again largely depend on whether the Russians want to play ball. The Russian air forces in Syria fly a lot of the same aircraft as their Syrian counterparts, which makes identifying who is in the air very difficult even with advanced radar. A no-fly zone would either mean the Russians in effect agreeing to constrain and turn on their own ally or the United States accepting that it's basically unenforceable unless they are willing to risk shooting down Russian aircraft, of course, which again seems unlikely.

4. Safe zones

The US could go forward with a plan to declare and defend safe areas within Syria where refugees could go. But that would require defending those zones, and therefore heighten the risk of military clashes with Russia. Safe zones also would not have a great punitive effect on Syria and would be expensive and difficult to enforce.

5. Ground forces

US Special Operations Forces, Marines and Army Rangers are on the ground in Syria. US forces are supporting local fighters as they prepare to launch an assault on Raqqa, the self-declared capital of ISIS in northern Syria. However, it is "extremely unlikely" that there would be any kind of large scale US boots-on-the-ground operation as seen in Iraq in 2003, because that would lead to an endless quagmire, not to mention (the US) would be invading areas where Russian forces hold ground.

Bottom Line

Trump is clearly about to take military action in Syria. But U.S. military action is not going to be against Assad, because Russia wants Assad to remain in power. The Russian stance sets US President Donald Trump's new administration on course for a head-on diplomatic collision with Moscow. Mr Trump is faced whether to openly challenge Moscow and risk deep involvement in a Middle East war by seeking to punish Mr Assad for using banned weapons, or to compromise and accept the Syrian leader remaining in power at the risk of looking weak.