Is it too late to stop Syria’s descent into hell? Since the uprising against the despotic Bashar al-Assad began in March 2011, 70,000 people have lost their lives, one million refugees have fled across the border into the neighbouring countries of Jordan, Lebanon and Turkey, and four million Syrians – a fifth of the population – have been internally displaced. In recent days, the Assad regime has been accused of using chemical weapons in Aleppo and the rebels tried (but failed) to assassinate the Syrian prime minister in Damascus.

The popular uprising long ago morphed into an armed insurgency, backed by a motley alliance of the United States, Europe, Turkey, the Gulf states and . . . al-Qaeda. Syria, a secular state, has been engulfed in the flames of a vicious, sectarian civil war in which both sides want to kill their way to victory. Viable solutions of the diplomatic, non-violent variety are few and far between. “Syria poses the most complex set of issues that anyone could ever conceive,” declared General Martin Dempsey, chairman of the US military’s Joint Chiefs of Staff, in March.

The clamour for a military intervention in Syria is getting louder – especially following the (as yet unsubstantiated) chemical weapons claims. On the right, there’s the US senator and Republican former presidential candidate John McCain, who, in recent years, hasn’t come across a war he didn’t want the US to fight. The Obama administration, McCain told NBC on 28 April, should arm the rebels, impose a no-fly zone and “be prepared with an international force to go in and secure these stocks of chemical and perhaps biological weapons”.

On the left, there’s the French philosopher Bernard-Henri Lévy, one of the driving forces behind Nato’s 2011 war in Libya. In an interview with me for al-Jazeera English, which will be broadcast in June, he said “there is no question” that a military intervention in Syria, beginning with a no-fly zone, is “doable”. When I asked him how he could be so confident, he shrugged: “Bashar al-Assad is weak . . . a paper tiger."

If only. Assad may be a loathsome dictator but that doesn’t change a central fact: that he continues to command the support of a significant chunk of Syria’s population (Alawites, Christians, some secular Sunnis). Nor does it change his air defences, which are far superior to those of Muammar al-Gaddafi, Saddam Hussein and Mullah Omar. Syria is believed to have up to 300 mobile surface-to-air missile systems and about 600 fixed missile sites. Oh, and did I mention the chemical weapons?

The experts are much more honest about the limits of military action than the Lévys and McCains of this world. Dempsey, America’s top soldier, has said that he can’t see a military option that would “create an understandable outcome”. His opposite number in the UK, General Sir David Richards, the chief of the defence staff, has told ministers, “Even to set up a humanitarian safe area would be a major military operation,” according to the Sunday Times of 28 April.

The reality is that even the best-intentioned humanitarian intervention could end up costing hundreds, if not thousands, of innocent lives. Those who flippantly claim that life couldn’t get any worse for the Syrian people should be reminded of Algeria (ten years; 200,000 dead), Lebanon (15 years; 170,000 dead), the Democratic Republic of Congo (ongoing; five million dead) and Iraq (ongoing; 600,000 to a million dead).

Let’s be clear: diplomacy, whether of the coercive or the non-coercive variety, isn’t a panacea. So far sanctions haven’t worked and the Russians continue to bat for Assad in the UN Security Council chamber.

But isn’t it depressing to witness how the west’s interventionists are always waiting for diplomacy to fail? Their targets – Slobodan Milosevic, the Taliban, Saddam, Gaddafi and now Assad – are always latter-day Hitlers: crazy, irrational, immune to political or diplomatic pressure. To negotiate is to appease.

It is a simplistic, Manichaean view of the world. Yet as the then leader of the Syrian opposition movement in exile, Moaz al-Khatib, acknowledged in September 2012: “Negotiation is not surrendering to the cruelty but it is choosing the lesser of two evils.” (Al-Khatib has since been smeared by some of his fellow rebels – most of whom, admittedly, crave a western military intervention – as an Assad apologist. He has had to stand down as opposition leader.)

Listen to Haytham al-Manna, the anti-interventionist spokesman for the opposition National Co-ordination Committee, whose brother was killed by the Assad regime. “We must adhere to a negotiated political solution in this difficult phase so as to give every Syrian a chance to see the end of destruction,” he wrote in the Guardian on 18 April.

“We cannot let the bloodbath go on like this,” Lévy told me. However, there is little evidence to suggest that sending in our bombers or arming the rebels will ratchet down, rather than ratchet up, the violence. Remember: weapons are fungible. We have no way of preventing the al-Qaeda-affiliated members of the opposition from getting hold of bombs and bullets supplied by Britain and France. Nor does anyone have a credible plan of action for the day after Assad falls.

The west should be pouring water, not fuel, on the Syrian fire. Our ministers should be putting pressure on, and offering incentives to, Moscow to detach itself from Damascus; our diplomats should be trying to convince the Gulf states to rein in the rebels, especially those of the ultra-Islamist, hand-chopping variety; our lawyers should be threatening Assad and his underlings with International Criminal Court indictments.

It may be that none of these options works. But, a decade on from the US-led invasion of Iraq, the alternative – all-out war – is too dreadful to contemplate.

Mehdi Hasan is political director of the Huffington Post UK, where this column also appears, and a columnist for the New Statesman. His new al-Jazeera interview series, “Head to Head”, will begin airing on 7 June