There is an air of nightmarish farce to the Syrian government's decision to hold a constitutional referendum at a time when it is subjecting one of the largest cities in the country to relentless, punitive bombardment. The agony of Homs, now in its fourth week, appears endless as President Bashar al-Assad's tanks pound residential districts indiscriminately. No one knows exactly how many died in Syria at the weekend but most estimates range between 60 and 90. Either way, hardly anyone in Homs was in any position yesterday to tick or cross Mr Assad's meaningless shopping list of reforms.

In any case, the President has already promised all or most of these reforms – fixed-term presidential mandates, multi-party elections and other gewgaws – raising the question of why a vote is being held. The answer to that, of course, is that the vote is another attempt to throw dust in the eyes of the international community and bolster the claim of the regime's allies in Tehran, Beijing and Moscow that Mr Assad needs time to execute his planned changes – time that will be used to flatten more of Homs, whose fate will then serve as a warning to other opposition strongholds in Syria of what they can expect if they continue their defiance.

We have been here before. In the Yugoslav wars of the 1990s, the world hummed, hawed, "condemned" this and that and from time to time roused itself to issue feeble-sounding threats while Slobodan Milosevic's forces rampaged from one city to another. It was only when they settled on the obstinate little town of Srebrenica in eastern Bosnia in 1995 and murdered 8,000 people there that the world finally acted. Belgrade then, like Damascus now, was liberal with promises to declare ceasefires, avoid civilian casualties, let in the Red Cross and – always a favourite phrase with dictatorial regimes – institute reforms. Then, as now, Beijing and Moscow professed to be impressed by these promises. Meanwhile, they did their best to stop any outside force from restraining the carnage on the grounds that it would constitute unacceptable interference in a sovereign state's internal affairs and make matters worse.

The lesson from that Balkan debacle is that sitting on one's hands and waiting for a natural equilibrium of power to reassert itself is not a strategy but a substitute for one. It can take a long time before civil wars burn themselves out, and the other great problem is that by then various unwelcome outsiders will have become involved, eagerly fighting their own proxy wars. Saudi Arabia's manifest desire to insert itself in the Syrian conflict on the side of the Sunni majority is only one of several alarming developments. The last thing that Syrians need is "liberation" at the hands of Sunni theocrats from Jeddah.

What to do? As Beijing often follows, or is a faint echo of, Moscow in these matters, all hope of co-ordinating a truly international approach to the Syrian crisis seems to depend on trying once again to get Russia to change course. This will be tough. Russia's rulers are prickly, defensive and feel slighted, not always without cause, most recently over Libya. But other options are scarce. It would be good to know that the US Secretary of State, Hillary Clinton, is working the phone line to Moscow hard in this respect, not simply adopting a high moral tone about Homs in her speeches.

It is vital that the West, which effectively means America, persuades Russia of the folly of continuing to back the regime in Damascus and gets it to throw its weight behind a negotiated compromise that involves elements of the regime, minus the Assad family, and the opposition. In the meantime, we need not dignify the referendum with a response. The time when such devices might have achieved anything in Syria, unfortunately, has long passed.