THE BRUTAL REGIME in Khartoum, the capital of Sudan, has orchestrated genocidal counter-insurgency war in Darfur for five years, and is now poised for victory in its ghastly assault on the region's African populations.

United Nations Security Council Resolution 1769, adopted in July, authorized a force of 26,000 troops and civilian police to protect Darfur's civilians and the humanitarian groups serving some 4.2 million desperate people. Without protection, these groups will be forced to withdraw. But Khartoum has obstructed the force authorized by the UN, and final success in these efforts seems within grasp. On Nov. 26, Jean-Marie Guéhenno, the UN undersecretary for peacekeeping, raised the prospect that the UN-authorized force for Darfur may have to be aborted because of Khartoum's actions.

Guéhenno asked a question that answered itself: "Do we move ahead with the deployment of a force that will not make a difference, that will not have the capability to defend itself and that carries the risk of humiliation of the Security Council and the United Nations and tragic failure for the people of Darfur?"

The unprecedented UN/African Union "hybrid" mission for Darfur (UNAMID) has been badly hurt by the refusal of militarily capable nations to provide the two dozen helicopters required, at the least, for operations in Darfur. No NATO country has offered even one helicopter - a sign that, despite fulsome rhetoric, these nations' real concern for Darfur is minimal. But it is Khartoum's brazen obduracy that threatens to leave the people of Darfur without protection.

Months after Resolution 1769 authorized the present peace support operation to Darfur, and more than a year after a previous council resolution authorized a similar operation, Khartoum is still objecting to the roster of countries that are to provide troops, police, and specialists. Khartoum refuses to grant landing rights to heavy transport aircraft or allow night flights (critical for both civilian protection and medevac needs); refuses to grant adequate access to Port Sudan; and refuses to grant adequate land or water rights in arid Darfur. Khartoum also demands the right to shut down UNAMID communications during its own military operations - an unacceptable condition.

What will happen if the UN gives up on UNAMID? Utter catastrophe. A weak, undermanned African Union mission currently serves as the only protection in Darfur. This demoralized force is barely functioning, simply trying to hold on until Dec. 31, when its mission is supposed to fold into UNAMID. But given Khartoum's obstructionism, this transfer will be at best symbolic: There may be UN sponsorship, but no meaningful deployment of UN troops or resources. Once it is clear that a meaningful UNAMID is not deploying, African nations will quickly withdraw their overmatched troops, which have already endured an unconscionable number of casualties.

With no international presence - by the UN, the AU, or aid organizations - nothing will constrain Khartoum, or the rebels, or various armed elements and bandits. Confrontations between Khartoum's forces, including its Janjaweed militia allies, and increasingly militarized camps for displaced persons will escalate quickly. Khartoum is likely to use its bombers and helicopter gunships in such battles, ensuring massively disproportionate civilian casualties.

UNAMID was badly conceived. Its command-and-control structure is ambiguous. It relies too much on African nations that cannot provide enough fully-equipped, self-sufficient troops and civilian police. The "hybrid" nature of the mission was itself a poorly calculated concession to Khartoum. But this mission is now the only arrow in the quiver: There is no other force on the horizon, no other means for protecting civilians and humanitarians. If NATO nations aren't prepared to provide 24 helicopters, they are hardly likely to participate in any non-consensual deployment of force to Darfur.

UNAMID must succeed. If it does not, how long it will be before Darfur slides into cataclysmic destruction, with no means of halting that slide? This is the stark choice before the international community: Is it prepared to see the mission fail? Or will it rally the resources and exert the pressure on Khartoum, both of which are critical to the mission's success?

Eric Reeves is a professor at Smith College.