AFULL ARSENAL of diplomatic tricks has been tried on behalf of Darfur, the western province of Sudan where the government is orchestrating genocide. A number of A-list statesmen -- Britain's Prime Minister Tony Blair, Secretary of State Colin L. Powell, U.N. Secretary General Kofi Annan -- have journeyed to Sudan to demand an end to the killing; still the genocide continues. Cease-fires, undertakings and protocols have been negotiated and signed; still the genocide continues. Two U.N. Security Council resolutions have condemned the government's behavior; still the genocide continues. Tomorrow and Friday, in a triumph of hope over experience, the Security Council will convene an extraordinary session in Kenya, hoping to shine the spotlight on Sudan's suffering. But unless the council members stiffen their rhetoric with sanctions, they will spotlight their own impotence.

Sudan's pragmatic dictatorship has bowed in the past to determined external pressure. It expelled Osama bin Laden and negotiated an end to its long-running war with rebels in the south, both thanks to the threat of sanctions. But Sudan's rulers do not make concessions if they don't have to do so, and they believe they can exterminate tens of thousands of people in Darfur and get away with it. When outsiders wax especially indignant, the junta signs another protocol and makes a tactical concession. But its strategy remains unchanged: to cement control over Darfur by decimating the tribes that back various local rebels.

The first phony concession came in April. Sudan's government signed on to a cease-fire, promising to "refrain from any act of violence or any other abuse on civilian populations." Since then the government has participated in unprovoked assaults on villages, murdering men, raping women and tossing children into flames that consume their huts. In July Sudan's rulers signed a communique with Mr. Annan, promising to "ensure that no militias are present in all areas surrounding Internally Displaced Persons camps." Since then militias have continued to encircle the camps, raping women and girls who venture out in search of firewood. In August Sudan's government promised Jan Pronk, Mr. Annan's envoy, to provide a list of militia leaders. No list has been forthcoming. Last week, in a concession that perhaps reflected nervousness about the approaching Security Council meeting in Kenya, the government signed two new protocols, committing itself among other things to "protect the rights of Internally Displaced Persons." A few hours later, government forces stormed a camp for displaced people.

In sum, the considered judgment of Sudan's rulers is that they can flout international commitments with impunity. Unless that judgment can be changed, the Security Council session in Kenya will not achieve anything. Sudan's dictatorship must be credibly threatened with sanctions that target officials responsible for war crimes, and these officials must also be made to face the possibility of prosecution. Beyond that, outsiders need to recognize that there is little prospect of security for Darfur's people -- and therefore little prospect of a return to destroyed villages, a resumption of agricultural production and an escape from starvation -- without a serious peacekeeping force. Gen. Romeo Dallaire, the U.N. commander in Rwanda during the genocide a decade ago, has suggested that a force of 44,000 is needed. Charles R. Snyder, the senior State Department official on Sudan, has estimated that securing Darfur would take 60 to 70 battalions.

More than a year and a half into Darfur's genocide, the United States and its allies have proved unwilling to consider that kind of commitment. They have moved at a snail's pace to support a 3,500-strong African Union force, which in any case would be inadequate; the record of deploying underpowered peacekeepers in war zones is that the peacekeepers get humiliated. The allies are starting to discuss another U.N. resolution, but this seems likely yet again to lack a real threat of sanctions. Up to a point, this is understandable: Security Council members such as China are opposed to strong action, and the United States is conserving limited military and diplomatic resources for Iraq and the war on terrorism. But Darfur's crisis is so awful that the usual balancing of national priorities is immoral. Some 300,000 people may have died in Darfur so far, and the dying is not yet finished.