The WFP has responded to the immediate crisis, providing two months of emergency food assistance to the Darfur camps in an attempt to persuade people to stay put. But this effort, I was told by a WFP official, is "not sustainable." So the WFP has also begun positioning food for the possible influx of tens of thousands of desperate refugees into eastern Chad. Mohammed Ahmed views this prospect with horror. "People moving to safety and food security from the Kalma camp (Darfur's largest) to eastern Chad would have to cover 500 kilometers, risking attacks from the Janjaweed and rebels in Chad near the border." It would be a long, dry, lethal march.

The international community, led by the United States, now faces a decision. It might be possible to back down from confrontation with Bashir in the hope that aid groups would be allowed to return. An atmosphere of heightened hostility also complicates the implementation of the peace agreement between Sudan's north and south, on which many lives depend. There is a humanitarian argument for this course. But it would confirm the effectiveness of Bashir's strategy of punishing the innocent and confirm the permanence of a violent and unjust status quo in Darfur.

Or the world can increase the pressure on Sudan's regime, knowing that Bashir may cause more short-term suffering and death as such pressure is applied. This approach can be morally justified only if there is a reasonable hope of eventual success. And this requires the development of a thoughtful strategy that leads, step by step, to a government in Sudan that values the people of Darfur and implements the north-south agreement in good faith. This does not necessarily mean regime change, but it probably requires Bashir change -- the emergence of a Sudanese leadership willing to start anew.

In this task, the Obama administration has two great advantages. The first is Bashir himself, whose unhidden, unhinged brutality is destroying the credibility of all who have shielded him in the past. The second is President Obama's extraordinary global standing, which he could use to persuade Europeans on broader economic sanctions and to peel off traditional Sudanese supporters such as Egypt. But this would require the immediate expenditure of diplomatic capital, the elevation of this issue in relations with both friends and rivals, and the possible use of military force down the road.

Not every global humanitarian crisis justifies this kind of commitment, else America would be endlessly overextended. But if genocide does not justify such action, it will never be justified. And we would lose the right to say, "never again." Michael Gerson's e-mail address is michaelgerson(at)cfr.org. (c) 2009, Washington Post Writers Group