SUDAN IS SET to acquire a new government of national unity today, a milestone in the implementation of the north-south peace deal negotiated with U.S. assistance and signed in January. John Garang, who for years led a southern rebellion against Sudan's northern government, will be sworn in as deputy president, and a constitution that provides for elections is supposed to follow. In an ideal world, this political opening would assuage rebel groups in the western territory of Darfur, whose violence has provoked a grotesquely disproportionate campaign of genocide by the government. But there's no guarantee that the consolidation of north-south peace will be good news for Darfur. The old regime's hardliners could easily embark on a new round of war crimes, making it impossible for Western governments to support the peace process and so condemning it to fail.

The most recent signs of these destructive impulses come not from Darfur but from Sudan's eastern region. According to rebel leaders there, the Sudanese government has responded to attacks on its troops by bombing civilians and destroying four villages. Neighboring Eritrea, which appears to support the eastern rebels, has accused Sudan of carrying out atrocities; Sudanese officials have retorted that Eritrean provocation may cause the situation on the border to "explode." The pattern of rebel activity followed by heavy-handed government response is eerily similar to the beginning of the genocide in Darfur.

Meanwhile the Darfur news is mixed. The World Health Organization recently reported a decline in mortality in some parts of the region, suggesting that the huge U.S.-led relief effort has reduced the death rate from appalling to just bad. NATO is preparing to airlift extra African Union troops into the region, part of a plan to expand the African Union presence from 2,700 to 7,700 personnel. Darfur rebel groups and the government signed a "declaration of principles" this week and a United Nations envoy said a peace deal was possible by the end of the year. But things could easily go wrong again. The government seems intent on razing the Kalma camp, a settlement with an estimated 120,000 displaced people. If the inhabitants are forced to return to villages that remain vulnerable to attack or outbreaks of infectious diseases, the death rate could head back up.

The keys to containing this suffering are the same as they've been for the past year. The relief effort needs to be sustained: France, Germany, Japan and Sudan's Arab neighbors should all give a lot more. The African Union deployment needs to be accelerated: Even a 7,000-strong contingent may be too small to protect civilians across an area the size of France. And Sudan's leaders need to get the message that the mass killing of civilians, whether through direct force or through the indirect tactic of destroying their shelter, will not be tolerated.

These are now the outlines of the Bush administration's policy, to its credit. But the test for the administration will be whether it invests enough energy in presenting Sudan with a unified message. Repeatedly over the past year, the international community has allowed Sudan to get the idea that the United States and its allies didn't really care about Darfur's civilians. The U.N. Security Council threatened to get tough, but then China blocked action; sanctions were threatened and then somehow forgotten; Darfur was emphasized and then subordinated to the north-south peace prospects. President Bush, who recently repeated that the Darfur killings amounted to genocide, must ensure that there is no ambiguity this time.