Syria's ceasefire began crumbling as soon as it started. Fighting continued in Idlib. Tanks still sit in Homs. And yet, Kofi Annan's peace plan is still seen as the only game in town. UN Secretary-General Ban Ki-moon insisted yesterday that "an opportunity for progress may now exist, on which we need to build".

The peace plan spells out a list of demands: a serious "political dialogue", the removal of government forces from cities and respect for right of protest. The problem is Assad cannot sincerely comply with these demands without committing political suicide.

Another unanswered question is who, exactly, will participate in this political dialogue. The formal opposition, dominated by the Syrian National Council, is mired in fratricidal bickering. Yet these squabbling factions have little idea of what's unfolding on the ground. The SNC is detached from the Free Syrian Army, which claims to be in charge of the military side. In reality, even the FSA is nothing more than a label of convenience for local fighters. How will they be bound to any settlement?

The third problem is that attitudes in Syria are hardening. The regime is dominated by the Alawite sect of Islam to which the Assad family, its cronies and key military commanders belong – but which comprises scarcely over a tenth of Syria's population. The spectre of a Sunni-dominated government, especially one that includes the most extreme strands of the opposition, is frightening to many Syrian minorities. Then there's the regional context. Syria's violence has spread to Lebanon and Turkey, and the old cross-border networks once used by al-Qa'ida in Iraq to pump fighters and weaponry from Syria into Iraq are being reactivated in reverse.

Could the answer lie in a regional solution? The Sunni powers of the Middle East, Saudi Arabia above all, know that toppling Assad will remove Shia Iran's only remaining friend in the Middle East. But for all their posturing, there's little evidence that many weapons have reached the rebels. Turkey has hinted of intervention, but it's unlikely to step up without allies in tow. The US and Europe are rightly leery of stepping into the swamp. This month being the 20th anniversary of the start of the war in Bosnia-Herzegovina, they rightly recall that the half-measure of "safe zones" are rarely that safe. But a full-scale invasion would be catastrophic.

Under the surface, the Assad regime is rotting. An orderly default, as the Annan plan envisions, would be nice. But this ceasefire is a mirage. When it breaks, the disintegration of Syria will resume.

The writer is a research fellow at the Royal United Services Institute