U.S. President Barack Obama faces few options and ample risk as he and his military chiefs mull a possible strike against Syria — and must first find a balance between doing too little or too much against the regime of Syrian President Bashar al-Assad.
A misstep in either direction could make the already gruesome situation in Syria and the surrounding region much worse, experts warn.
Obama said Friday he is considering "limited, narrow" military intervention but has ruled out a regime-changing "boots on the ground" invasion.
U.S. and European officials say a short, sharp attack is the preferred response to what they believe is Assad's responsibility for a chemical weapons attack on rebel-held areas last week.
Obama's options are "fairly limited" said Christopher Chivvis, senior political scientist with RAND corporation, a global policy think tank, if his only goal is to punish Assad and deter the use of chemical weapons.
"You're talking pretty much about strikes against command and control sites," Chivvis told CBC News.
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But even those attacks — which would most likely be limited to Tomahawk cruise missiles, launched by U.S. warships from outside Syrian airspace — must be careful not to do too much damage in case the need arises for further strikes.
"The regime needs to have something to lose," for strikes or threats to be effective, said Chivvis.
If the U.S. takes on the broader goal of more actively assisting the Syrian rebels it would likely expand its attacks to include regime runways, aircraft and other targets, he added.
Attacks on chemical weapons sites also carry the risk of releasing toxins into the air, possibly killing the very civilians the military intervention is meant to protect.
Likewise, if any technicians from Russia, a major arms supplier to Assad, were killed, this would inflame already troubled Western relations with Moscow.
"Once people are being killed you never know where that mission, that sort of event, might go," cautioned retired general Rick Hillier, Canada's former chief of defence staff, in a recent interview with CBC News.
"We have to be certain what we are trying to achieve. Because in the end, you will kill people and you will put other people at risk," he added.
Prime Minister Stephen Harper on Thursday said Canada has no plans for a military mission of its own against Syria, though Ottawa supports its allies and is convinced of the need for "forceful action."
Destroyers in Mediterranean
The U.S. Navy has four destroyers in the eastern Mediterranean, equipped with cruise missiles, and is presumed to have also sent in a number of similarly armed submarines, though their locations are kept secret. Two U.S. aircraft carriers are in the region, as is a recently refitted French carrier.
The U.S. could have as many as 200 missiles available in the region, roughly twice the number that were fired against Libya in 2011, according to one estimate. Those strikes helped change the course of the Libyan civil war.
The U.S and France — so far the only other country willing to take part in attacks — could also fly manned aircraft out of airbases in Turkey, Jordan and the United Arab Emirates.
U.S. F-16 jets have remained in Jordan after an exercise earlier this year while B2 long-range bombers could fly from the continental United States, unseen by Syria's radar and considerable air defences.
The use of manned aircraft puts military personnel in greater danger, however.
"No one wants the risk of pilots being captured or killed,"one European defence source said on condition of anonymity.
Without some action soon, officials worry that Assad will feel he can resort to chemical weapons again with impunity — despite Obama's declaration last year that their use would cross a "red line" that would require strong action.
Some also fear lack of sufficient action in Syria could cast doubt over other U.S. "red lines," encouraging Iran to pursue its nuclear program, which Tehran says is peaceful but the United States and its allies believe aims to produce weapons.
Any failure to strike Syria could also prompt Israel to take matters into its own hands, causing yet more upheaval in an already highly unstable region. Israeli jets have already raided Syrian targets on several occasions.