The ballots have been tallied and the results are in: Southern Sudanese voted overwhelmingly for independence from the government in Khartoum. With a total turnout of 97 percent and 99 percent of voters casing their ballot in favor of secession, southern Sudan is on its way to becoming the world’s newest country.

Yesterday, President Obama congratulated the southern Sudanese on “a successful and inspiring” referendum. The symbolism of the event is remarkable: After decades of war and marginalization by the north, southern Sudanese have finally achieved self-determination. Furthermore, the referendum was largely conducted without major incident. Sudanese President Omar al-Bashir has acknowledged the will of southern Sudan and has welcomed amicable relations with its former adversary in the future.

Unfortunately, there is plenty of cloud surrounding this silver lining. Sudanese troops are still stationed along disputed border areas. This past weekend, 50 people were killed by Sudanese soldiers along the border in Makalal. Ongoing issues concerning border demarcation, citizenship, debt negotiations, conflict in Darfur, infrastructure and development in the south, and the establishment of a stable government in Juba will take a long time to reconcile.

Though the turmoil in Sudan was largely neglected by the Obama Administration until a few months before the referendum, Washington is making up for lost time. The United States continues to be the largest contributor to Sudan, having given $6 billion since the Bush Administration aided in the creation of the Comprehensive Peace Agreement five years ago. The Obama Administration has developed an agenda for U.S. engagement with Sudan up to the south’s official independence on July 9. However, the Obama Administration should keep contingency plans ready should the situation deteriorate. It should also devise plans for relations after July 9 that take account of a series of possible outcomes ranging from the ideal to the disastrous.

Today’s celebration in the streets could quickly turn into instability and conflict tomorrow, and the United States should be ready to respond if the need arises.