All blame game, no solutions

Just who is responsible for what atrocity, however, has never been easy to establish in this most propaganda-driven and opaque of conflicts, and already a fog has begun to settle over this week's massacre.

What appears beyond reasonable doubt is that the victims, who may number as many as a thousand, met fates consistent with exposure to a nerve agent. Many died while asleep, and survivors reported difficulties in breathing, and of seeing relatives collapsing inexplicably and without warning. Activists who alerted the world to the carnage have blamed Assad's forces. They, just as impulsively, have denied it.

Unlike the rebels, the regime possesses nerve agents like sarin, mustard gas and VX and the means to weaponise them - and it has a proven record of deliberately targeting civilians it believes are sympathetic to the rebels. Given that, it might seem reasonable to presume that it was responsible for Wednesday's attack. An independent investigation would settle the matter, and as it happens a United Nations team arrived in Damascus last weekend to investigate allegations of chemical weapons attacks. However, the regime has refused the team permission to visit the sites where this week's attacks occurred.

Given the Islamic tradition of quick burial and the fact that nerve agent residues fade after 48 hours, it may never be conclusively established that this was a poison gas attack. Nevertheless, it corresponds with reports that other, smaller gas attacks have occurred with increasing regularity - reports which the UN team was set to investigate.

Speculation has arisen as to why the regime might launch the deadliest poison gas attack since 1988 (when Saddam Hussein slaughtered 5000 Iraqi Kurds) a year after Barack Obama warned that the use of chemical weapons would be "a game changer''. Does Mr Assad believe that Mr Obama was bluffing? Quite possibly, since Mr Obama failed to make good on his warning after evidence that Syria had crossed the "red line'' by launching smaller chemical attacks. The White House's reluctance to condemn the overthrow of Egypt's President Mohamed Mursi may also have influenced the thinking of the Syrian regime. Egypt's military acted only because it had the support of Saudi Arabia, Kuwait and the United Arab Emirates - and a promise from those nations of $US12 billion ($13.3 billion) in support.

Fears that a successful rebellion in Syria might inspire uprisings elsewhere in the region have translated into surprisingly strong support for Mr Assad, and he is in the handy situation of being able to count on the backing of China and Russia in the UN to forestall condemnation and intervention by that body. Indeed, the Kremlin has even suggested the latest attacks might have been "a provocation'' by rebel forces, an attitude probably inspired in large part by US anger over Russia's refusal to extradite whistleblower Edward Snowden.

Mr Obama's refusal to condemn earlier, less serious, gas attacks suggests he now regrets talk of "red lines''. But international pressure for action, contingent on the reports being true and led (unexpectedly) by the French government, has already begun. Mr Obama has responded by ordering US intelligence agencies to verify whether the deaths were the result of poison gas. Whatever action he ultimately takes, however, will be guided by domestic considerations, and for the moment there is no appetite whatever for a new military intervention in the Middle East. Nor is there any pressing national security reason for the US to intervene. Such is the calculus of realpoliltik.

The United Nations remains a possible agent of response, but only if the Security Council allows it. That looks unlikely given the intransigence of China and Russia. If ever there was a case of the UN to act on its Responsibility to Protect protocols, it is now. China and Russia must recognise this or stand accused of aiding and abetting genocide.