A power-grab by rebels would come with huge civilian casualties and also set a bad precedent in a country with long ethnic rivalries, lacking a professional military and with an armed civilian population.

South Sudan is on the verge of a new civil war. Without a swift, internationally-led effort to contain the ambitions of key protagonists, the crisis emanating from last week’s putsch could spiral out of control, creating a new humanitarian crisis in a continent reeling from the wars in Mali and Central Africa Republic, and itinerant conflicts in Somalia and Congo.

The country has been on the knife edge for months as President Salva Kiir systematically dismantled the institutions that gel its previously warring tribes. While aware of long festering tensions, South Sudan’s important partners wrongly assumed that President Kiir’s opponents would never present an imminent threat to his hold on power as they did early this month.

Neither did Kiir, who, despite his dismal failure to transform this poor country, had successfully played tribal politics in a way that safeguarded national unity and his legitimacy. But his cabinet reshuffle in July, in which he sacked his deputy Riek Machar and all other independent leaders, upset the political fabric. It remained a matter of when, not if, Kiir’s opponents and their heavily militarized supporters would rise up against his rule. Unlike in the past when rival militias clashed at the slightest provocation, the dissidents pressed their interests through SPLM party organs, where they had an upper hand.

But sensing that his own decisions were to be reviewed at the December 14 party conference, for which the Machar camp had psyched the country, President Kiir scuttled the meeting, forcing his opponents to walk out. It is Kiir’s subsequent execution of one of the dissidents’ core demands – the disbandment of the Presidential Guards, the president’s security unit – that precipitated the violence. The government says that soldiers from Machar’s Nuer tribe refused to be disarmed, but the Nuers claim that only they were being disarmed.

The president’s opponents view the Guards unit, which the President created outside military structures, as a militia force that would enforce Kiir’s edict in the 2015 general elections. Kiir’s agreeing to disband the Guards is an acknowledgement of the need to heal rifts he had created in the military. He should now take further steps to reduce tensions: free leaders detained since the crisis began; recognize that politicians opposed to him, such as Machar, Rebecca Nyandeng, and SPLM secretary general Pagan Amum, will be allowed to organize and contest 2015 elections; and commit to a framework for free and fair elections.

Rather than weakening the President’s hand, these measures would reverberate across the land and deny the rebels the political cause they are using to rally supporters. The President should also cease the aggressive portrayal in state media of this crisis as ethnic warfare between Dinka and Nuer groups, which is giving the violence a tribal tinge on the ground at huge cost to innocent civilians.

Such basic resolution of the political underpinnings of the conflict would constitute a ceasefire on the government’s part, thereby helping reconcile communities and allow for mediation on the basis of one, united South Sudan. South Sudan’s size, infrastructure and resources cannot sustain the kind of dictatorships that prevail in neighboring countries.

A power-grab by rebels would come with huge civilian casualties and also set a bad precedent in a country with long ethnic rivalries, lacking a professional military and with an armed civilian population. The rebels’ ostensible camaraderie with Dinka leaders would not erase the suffering of ordinary Dinkas, whose soldiers and other elites are determined to fight on the government’s side. The takeover would herald another phase of the conflict – which is about how power and resources should be shared in South Sudan.

For too long, western powers paid attention to South Sudan only in terms of its relationship with Sudan. The rampant corruption, souring ethnic relations and limited transformation despite the west’s investment, were glossed over. President Kiir gambled with key decisions, from his choice of officials to cancellation of oil agreements that caused the state huge economic losses.

Instead of addressing the grievances of his opponents, the president moved to isolate them and their communities. He portrays the crisis as a Nuer rebellion, yet in his jails are leaders from all ethnic groups. Perhaps with the exception of his new deputy James Wani, Kiir has sacked from government all leaders who rose to prominence before his presidency. Many of them are now detained.

By laying responsibility for the conflict with Machar and the Nuer tribe, and not the other national leaders whom he has detained since the crisis, Kiir is replaying a decades-old script to isolate the Nuer, who, since the ethnographic work of Sir Edward Evans-Pritchard, were depicted by Anglo-Egyptians and Sudanese officials as warlike, aggressive and expansionist. There are awful memories too, most horrific being the 1991 clash between Machar’s and Garang’s forces in Bor, which left hundreds of Dinka civilians dead.

Machar tried to overcome this record by serving Garang and Kiir loyally for over a decade, in the process marshalling new Dinka supporters and leaders from other nationalities. With the ever coy Kiir, however, his negatives as an ambitious man festered, until Kiir sacked him this July. His rapprochement with Garang’s associates in recent months, while openly campaigning for the presidency, further cemented Kiir’s determination to remove him.

There is a lot more at stake in this crisis for all South Sudanese people, as well as countries in the region that would be sucked into a prolonged war, than merely the interests of two leaders fed up with each other. With the SPLM in limbo, there is no institution in the land that can mediate between the two sides. The African Union and UN should urgently find a mediator to formulate a way out of the crisis and towards a future of democratic inclusiveness, peace and prosperity.