As his country slides back to civil war, the President of Sudan, Omar al-Bashir, has denounced Western moves to intervene as a colonialist conspiracy and likened Khartoum’s situation to Lebanon’s a month ago. It is true that villages in Darfur are being bombed — by Sudanese government aircraft. And it is true that troops are massing for a major offensive; these are Sudanese army troops. But what truly distinguishes this crisis from any other international emergency, and shames those leaders apparently willing to let it run its course, is genocide.

The remorseless “ethnic cleansing” of the black Sudanese tribespeople of Darfur constitutes the worst atrocity in Africa since the Rwandan genocide of 1994. At least 200,000 villagers — and possibly double that, according to credible US estimates — have been killed by government-backed Janjiwid militias. Two million survivors of their raids are homeless. A lull in the slaughter followed a peace deal brokered this year between Mr al-Bashir and one of three main rebel groupings ranged against him in Darfur. But he now appears determined to exploit the West’s preoccupation with the Middle East and Afghanistan, and finish what the Janjiwid began.

The tools available to stop him do not inspire confidence. With the mandate for an ill-supplied and ineffective African Union peacekeeping force due to expire on September 30, the United Nations Security Council has approved a resolution to replace it with a far larger UN force. But diplomats made clear that that force would not be deployed without Mr al-Bashir’s consent, which last week he withheld. And yesterday he insisted that the AU force could only stay on if it was not part of a larger UN deployment.

Aid agencies run ever-greater risks delivering food and medicines to Darfur, where 12 of their workers have been killed this year. Acute shortages have swelled refugee camps across the border in Chad, while those who have stayed behind are dying at an alarming rate. They may not have been shot by his army, but Mr al-Bashir is complicit in their deaths. Yet he is as unmoved by the latest UN resolution as by ten others that he has ignored during this crisis, and last week he received a senior US envoy but offered no hint of compromise.

Sudan has correctly judged that even if the UN had the stomach to attempt to send a peacekeeping force without Khartoum’s consent, the logistical obstacles to deploying a multi-national force of 20,000 in a desert the size of France would prove insurmountable. Sudan will also remain impossible to isolate internationally as long as Qatar, representing the Arab League, continues to support it in the UN out of misplaced ethnic solidarity; and China continues to abstain in relevant UN votes out of fondness for Mr al-Bashir’s oil reserves.

A UN meeting on Darfur is scheduled for Friday. It is not too late to reach a deal on humanitarian aid corridors; nor for the Arab League to see that defending barbarity is ultimately self-defeating. In the meantime, the next Rwanda looms.