The 2005 "Comprehensive Peace Agreement" (CPA) between the present National Islamic Front/National Congress Party (NIF/NCP) regime in Khartoum and the southern Sudan People's Liberation Movement (SPLM) ended one of Africa's longest civil wars, with nominal agreement on security, wealth sharing, and governance issues.

However, the international community - including the African Union, the U.S., the EU, and China - has not taken implementation of the peace agreement seriously enough for oil-rich Sudan. This has enabled Khartoum to renege on key elements of the agreement with little consequence and to manipulate ethnic, political, and military tensions throughout the region.

Without meaningful pressure, the NIF/NCP regime has also delayed the legislation that will guide a referendum in which South Sudan votes on whether to secede or remain part of a unified Sudanese state. The vote is scheduled for January 2011, but referendum legislation is already two years behind schedule.

The self-determination vote is critical for all of Sudan, and if compromised, southern Sudanese are likely to consider this the final straw and resort to renewed war to gain the independence the majority seeks. In anticipation, Khartoum may launch a preemptive military campaign.

This is particularly bad news

Potential war could quickly escalate to include other marginalized regions within Sudan, including the Darfur region of western Sudan. Conflict there over the past seven years has already led to the death of hundreds of thousands of civilians and displaced some 3 million people.

Increased tensions throughout Sudan make it probable that if the 2005 north/south peace agreement collapses, Darfur's massive conflict will be but one component of the first nationwide war in Sudan, The potential of such conflict to destabilize the country and the region can hardly be overstated.

Who else would participate in a war in Sudan? Tensions are high in the Nuba Mountains and southern Blue Nile regions, as well as in eastern Sudan. Although lying geographically in northern Sudan, all were allied with the SPLM during the civil war that raged from 1983 through the peace agreement of 2005. More than 2 million people died, and as many as 5 million were displaced - and much of the worst fighting occurred in these areas.

That's why Khartoum's refusal to demarcate the north/south border, one of its most fundamental obligations under the terms of the 2005 agreement, is of urgent concern. This refusal has led to dangerous military escalation on both sides of a region lying in the midst of Sudan's very large oil reserves.

The regime's military strategy in the event of war would probably be to control as much of the southern reserves as possible and create a vast defensive perimeter. Southern resistance would almost certainly be fierce and civilian casualties heavy.

Complicating the political situation, national elections for all government offices are also fast approaching. Though scheduled for April 2010, deliberate delays by Khartoum have made them logistically impossible. Signs already indicate that these elections will not be free and fair but rather an occasion for the regime to use its control of the electoral machinery and its vast patronage system in an effort to retain power and to regain international legitimacy.

Indeed, electoral interference has already begun in earnest. The Carter Center, for example, reports that its election monitors have not been accredited to observe the huge voter registration drive now under way.

Although the leadership in South Sudan has made its share of mistakes, it is not guilty of the massive bad faith that we see from Khartoum. Still, the reason Sudan is poised to explode lies in international failure to hold the regime to benchmarks and commitments that are clearly spelled out in the 2005 agreement, and others.

What should the international community do? Secretary of State Hillary Rodham Clinton announced a Sudan policy last month that aims for "a definitive end to conflict, gross human rights abuses, and genocide in Darfur" and "implementation of the CPA that results in a peaceful post-2011 Sudan or an orderly transition to two separate and viable states."

Confidential punitive and encouraging measures targeting Khartoum supposedly provide the leverage for these goals. But while this policy might be fine in the abstract, the notion that the U.S. can fine-tune selective unilateral pressures and incentives in a way that will change the regime's behavior in time to create a conducive electoral environment and avert war seems dangerously naive.

U.S. pressures and incentives must be accompanied by corresponding diplomatic investment in moving key international actors to demand that Khartoum fulfill its obligations under the peace agreement. An arms embargo on all of Sudan is a key first source of leverage, especially since China is the primary supplier of weapons that clearly violate the current U.N. arms embargo on Darfur.

The EU should do more to squeeze commercial and capital investments benefiting only the northern economy, and to end violations of its own arms embargo on Sudan. Britain and Norway were both instrumental in negotiating the 2005 peace agreement, and should be pushed to serve as guarantors for its implementation. Kenya was also a key CPA negotiating partner and has a clear interest in preventing resumption of war to its north.

Unfortunately, the African Union Peace and Security Commission has been ineffective in confronting Khartoum over its failures to honor the CPA; it must be made to see how disastrous resumed conflict in Sudan would be for the credibility of the organization.

Eric Reeves is author of "A Long Day's Dying: Critical Moments in the Darfur Genocide."