Long-simmering ethnic tensions in the South are boiling into unrest -- stoked, according to many in the Southern capital of Juba, by a Khartoum government unwilling to contemplate the oil-rich South's seemingly inevitable secession.

A massacre in Warrap state on Jan. 7, that left at least 139 dead and nearly 100 injured, was the latest clash between the two dominant tribes in the South -- the Nuer and the Dinka. While ostensibly due to a dispute over cattle, Sudan watchers say that the clashes have taken on an ominously political bent. Women and children are figuring prominently among the deaths reported in villages around South Sudan, according to Medecins Sans Frontieres, which suggests that settling political scores, not stealing cattle, is the primary objective of the raids.

These tensions are exacerbating a struggle for power and control of the Southern votes in upcoming national elections that will precede the referendum on independence by a year. Rival political and ethnic groups are clamoring for a greater role in national politics, even though secession seems inevitable. For them, according to the International Crisis Group, it is a last-gasp opportunity for local ethnic leaders to play a role in the coalition government established between the Southern rebels and the power center in Khartoum. It is also a chance for them to curry favor among the guerrilla soldiers who, though still under the command of the Sudan People's Liberation Army (SPLA) in charge of security in the South, have become uniform-wearing members of the Sudanese armed forces.

Payment of these soldiers is sporadic and incomplete, leaving many in uniform, like their civilian counterparts, increasingly disenchanted with the Juba leadership.

Such a potent mix of political tension, mounting ethnically motivated violence, and entrenched poverty has brought Africa's largest country to a crossroads, with an acute risk of destabilization -- and even the return to civil war.

"Two landmark events -- April 2010 national elections and a January 2011 referendum where Southerners will vote on whether to remain part of a united Sudan or secede -- could well result in further instability if all actors are not well-prepared," said a report jointly released (.pdf) by Oxfam, the International Rescue Committee and eight other international NGOs on Jan. 9. "Failing to act is not an option," the report concluded.

The recent fractious negotiations over the shape and wording of new electoral laws underscore the fragility of the peace agreement reached in 2005 to end more than 20 years of ruinous civil war.

More than 200 opposition loyalists were blasted with tear gas and beaten with sticks and batons during a Dec. 14 protest in Khartoum in support of political reform ahead of the polls. As news of the protest trickled out of the capital, scores of opposition demonstrations erupted nationwide, led by South Sudanese who risked being excluded from the historic votes.

An amended version of the electoral law was forced through by the ruling National Congress Party in the wake of the demonstrations, which earned the Khartoum government withering criticism from the United States. Washington is itself facing heavy international scrutiny over its reformulated Sudan policy, which activists have complained offered "too much carrot and not enough stick" to the Khartoum government.

But in a move applauded by the U.S. special envoy to Sudan, Scott Gration, as "a positive step towards CPA implementation," the NCP again modified the bill in response to pressure from Washington. In its final ratified form, approved on Dec. 29, the law allows displaced Southerners living in the North to vote in both the upcoming election and the subsequent referendum for secession.

Such a concession has been considered crucial by political analysts for the voting to be legitimate. On the other hand, whether the elections and referendum will ultimately be free and fair remains to be seen. Analysts, meanwhile, have warned that any hint of meddling in the polls by Khartoum would hasten a unilateral Southern decision to secede, thereby prompting a return to war.

In his Jan. 3 address to the nation, President Omar al-Bashir sought to dispel the concerns expressed both in the South and worldwide about the prospects for the next 12 months, vowing to achieve a comprehensive peace in Sudan through "transparent and credible elections." However, as an indicted war criminal who has thus far evaded arrest over charges of war crimes and crimes against humanity for his complicity in the crisis in Sudan's western region of Darfur, Bashir perhaps has different standards for "transparency and credibility" than his international interlocutors.

Beyond the elections, additional challenges that could further threaten the uneasy peace in Sudan remain, including the implementation of a controversial International Court of Arbitration ruling on the demarcation of the oil-rich town of Abyei and the still-unsettled question of the boundaries between North and South.

Meanwhile, the fragility of the humanitarian situation in South Sudan also risks deteriorating from crisis into full-blown catastrophe, according to the aid organizations operating there. It is with these concerns in mind that U.S. Secretary of State Hillary Clinton on Jan. 8 called on all parties to "rise to the challenge with political will and vision."

"The parties of Sudan cannot afford to delay and there can be no backtracking on agreements already reached," she said. "The risks are too serious."

**Lauren Gelfand is a freelance journalist and analyst now based in Nairobi, with an interest in security and defense issues. After beginning her career as a wire service correspondent, working on three continents for Agence France-Presse, she currently serves as Middle East and Africa editor for Jane's Defence Weekly magazine. She writes in French and in English for a variety of publications.