Western agonising over Syria, underlined by the divisions among European foreign ministers yesterday, mirror the painful realities over two years after the uprising began against Bashar Assad’s dictatorship.

After more than 70,000 deaths and a hideous humanitarian and refugee crisis, Assad is still there. The rebels are not sliding to defeat. But ruthless use of the regime’s relatively formidable military machine has helped to maintain its control over many parts of the country in the face of a determined but also divided rebellion.

This was the context for William Hague’s arguments in favour of the Anglo-French proposal to lift the European arms embargo, if not yet actually to arm the rebels. They have been reinforced by the conviction among British officials – partly based, they say, on unpublicisable intelligence – that the regime has already used chemical weapons. And he has continued to insist that the threat of supplying arms to his opponents is necessary to force Assad to negotiate in earnest.

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But it is equally the context for the fear among some of his European counterparts that such supplies would, if actually delivered, simply escalate into a new Syrian arms race, leading to more deaths, bloodshed and suffering. And the doubts about preventing weapons falling into the hands of extreme Islamist groups, including ones affliated to al-Qa’ida – doubts shared in Britain, incidentally, by a Labour Party in gradual retreat from its recent past doctrine of liberal interventionism – are real enough.

The search for some form of “limited” military intervention has long exercised Western diplomats. And there are equally telling objections to the alternative of a no-fly zone, including the US military’s argument that only a relative small proportion of Assad’s firepower has so far been delivered by air, and the worries about penetrating an air defence system far more sophisticated than Muammar Gaddafi’s. (The notion of attacking such defences with Tomahawk missiles is said to have come up against – among much else – the allegedly sizeable presence of Russian military advisers vulnerable to such attacks).

Yet despite President Obama’s deep resistance to further military intervention, freely attested in Whitehall, the West might already be stumbling into an intervention of some kind, had the US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov not agreed three weeks ago on efforts to bring Syria to a peace conference in June. Last night’s Paris dinner between Kerry, Lavrov, and the French foreign minister Laurent Fabius was an attempt to take this delicate process a stage further.

All those at yesterday’s Brussels meeting are agreed that such a conference – to which the Syrian regime has now assented “in principle” – is highly desirable. The division was over whether the Anglo-French call to lift the embargo would assist or – as other European ministers argued yesterday – endanger such a process. There is persuasive support for the latter view in a sober new European Council for Foreign Relations assessment that argues against “arming for peace” and for the west instead to prioritise “de-escalation” of the war. Sober because it recognises that the “political approach” it favours is itself fraught with difficulties, will involve “unpalatable compromises” if it is to get anywhere, and “will clearly not have immediate results on the ground”.

But the report’s authors, Julien Barnes-Dacey and Daniel Levy, argue that western players should break out of the “make believe” choice between “military intervention lite” and “diplomacy lite”. And while they are not explicit about this, their arguments also militate against the attempt to combine both courses, which has appeared to inform French and British government attitudes in recent weeks.

Instead, they contend, the real and “ugly” choice is between full scale military intervention and the “real diplomacy” for which the Russo-American proposal affords the first tentative opportunity. Since the first is rightly out of the question, post-Iraq, the choice of a genuinely inclusive diplomatic initiative is the best, perhaps the only, alternative hope of “de-escalation”. Where the ECFR paper most sharply differs from conventional wisdom in western capitals is by arguing – and these are the “unpalatable compromises” – first that external players accept that the fate of Assad should be an issue for transition negotiations, rather than making his removal a precondition of them taking place; and secondly that Iran should be brought into the process.

Underlying western support for the rebels is not just fully justified horror at the brutality of Assad’s suppression of the revolt, but a strategic desire, as Tehran well knows, to detach Iran from Syria and – when it is seeking to confront it on nuclear weapons – to weaken its influence in the region. It’s hard to see just how that goal is to be pursued in the current military stalemate in Syria, or how progress can be made without Tehran or Moscow (which is pressing for the inclusion of Iran) having a real stake.

The ECFR paper argues that such a process should also include on the pro-rebel side Saudi Arabia and the Islamist opposition group Jabhat al-Nusra, which is proscribed by the US. Such an inclusive – and probably continuous – process starting next month should be pursued not for reasons of “moral clarity” or “political popularity,” but because it offers the best chance of at least beginning “to reduce the devastation, killing, and chance of regional contagion”. Iran has claimed to support the idea of a peace conference. There may now be little alterative to putting Tehran to the test.