“I STICK my neck out for nobody,” drawls Rick in “Casablanca”. “A wise foreign policy,” says Captain Renault. But is it? Over the past ten months Syria has slid to the brink of civil war. Firefights, ambushes, massacres and bombings take place almost daily. Defying international sanctions, the regime kills protesting citizens by the dozen. The opposition, once hostile to all violence, has started to take up arms that increasingly pour in from neighbouring Lebanon. Aided by army defectors, it gains and loses control of small patches of territory, but it will not soon win the upper hand without more help.

Some outsiders, including the emir of Qatar and a growing number of analysts at American think-tanks, have begun to call for military action. One argument for intervention is consistency: the bloodshed in Syria is even worse than it was in Libya under Qaddafi. If outside powers have a responsibility to protect people from a mass-murdering tyrant, then surely Syria, where more than 5,000 have been killed in a campaign of state violence, is a prime candidate. Another is that several regional powers are already backing proxies in this fight. Iran and Russia aid the regime; Saudi Arabia and Turkey favour the rebels. Left alone, the rival camps will fuel a worsening conflict that could destabilise the entire region.

Damnascus

Military action would satisfy the understandable desire to do something—anything—in the face of terrible suffering. But it is unlikely to bring the conflict to a quick or satisfactory end, not least because opponents of the regime are divided. Dissidents have formed clashing camps and defectors follow rival officers, each commanding only a few hundred men.

There is no workable plan for an intervention. A no-fly zone would be useless, as the Syrian air force has not flown. Safe havens near the borders could protect citizens but they would soon need defending against regime troops. Striking the army—as in Libya—is an option but would not change the overall situation. Unlike in Libya, no unified rebel force is ready to sweep into the capital, secure the streets and take control.

Even if there were a plan, the cost of a botched intervention would be far higher in Syria. Like Iraq, where the American invasion of 2003 ignited a conflict that killed more than 100,000 people, it has a complex ethnic and sectarian make-up. Perhaps selective strikes on the regime's most brutal and murderous troops could stop some of the killing and weaken morale among Syria's rulers—but then again, it might just as easily persuade Bashar Assad to kill even more ferociously.

Military intervention does not make sense unless it has the legitimacy of widespread international backing and the likelihood of success. As yet, it has neither of these things.

Instead, therefore, the outside world must pursue diplomacy. Just now the opposition's most likely source of outside support is the Arab League, which sent an unarmed observer mission to Syria last month. Predictably, the mission failed to stop the killing. Since then, six Gulf states have withdrawn their members—and rightly so, given that the regime used the observers as cover for its violence.

Yet the mission has set the stage for the Arab League to call on the UN Security Council to endorse a plan under which Mr Assad would transfer power to his deputy in two months and conduct elections in five. This too might fail, but it heightens diplomatic pressure on Mr Assad's remaining supporters abroad, especially Russia.

Russia will soon have to choose between its troubled ally and the rest of the region. Although it has just sold $550m worth of fighter jets to Syria, its support of the regime has weakened slightly this month. It may eventually be persuaded to back a deal similar to one that this week ended a violent stand-off in Yemen. Under the auspices of several Gulf states, the Yemeni president, Ali Abdullah Saleh, received immunity from prosecution in return for going into temporary exile to allow for a peaceful transition of power.

In Syria that will take time, if it happens at all. Meanwhile, Western countries should help the opposition groups with sanctions and supplies such as medicines. Such aid is modest and piecemeal, but at least it will not make things worse.