analysisBy Berouk Mesfin
For the past five months, the government and opposition forces in South Sudan have been locked in a destructive political and military crisis.
Diplomatic efforts have thus far failed to secure a lasting ceasefire - let alone lay the groundwork for a negotiated political settlement. As a result, the volatile security situation in the Horn of Africa has only worsened.
Indeed, the crisis has added a new dimension to existing tensions in the region - between Uganda and Sudan on one hand, and Ethiopia and Eritrea on the other.
Every day the crisis continues, additional pressure is placed on these states that have, for some time now, been locked in a distrustful and suspicious relationship to support one side or the other.
As one official involved in the ongoing diplomatic efforts pointed out, 'the longer the conflict drags on, the more the possibility of fixing South Sudan fades, and the higher the risk of greater regional competition.'
There are obvious tensions between Sudan and Uganda - which no longer share a land border, and are respectively South Sudan's oldest enemy and closest ally.
Uganda has security-related, political and economic interests, which prompted it to intervene militarily in South Sudan in support of the government.
Historically, Uganda provided substantial support to the Sudan People's Liberation Movement (SPLM) during its armed struggle against Sudan, which reciprocated by giving support to the Lord's Resistance Army (LRA).
Uganda also sought to protect its lucrative bilateral relationship with South Sudan since it had recently become a major trading partner, to the detriment of Sudan's geopolitical and economic interests.
It also aimed to protect the thousands of Ugandans working and operating businesses in South Sudan. Ugandan President Yoweri Museveni assiduously cultivated close personal ties with South Sudanese President, Salva Kiir.
The scenario most feared by Uganda is an outright victory by the opposition forces, which are heavily linked to the Nuer ethnic group and led by former vice-president Riek Machar - also from the Nuer group.
This would lead to Kiir's removal from power, which would be a strategic setback to Uganda and erode its capacity to influence future developments in South Sudan.
The proximity of Ugandan forces to the oil fields in the Unity and Upper Nile states caused great anxiety in Sudan regarding Uganda's intentions.
Sudan was deeply concerned by the possibility that the Sudan Revolutionary Front (SRF), a coalition of armed groups opposed to Sudan, might receive a significant number of weapons from Uganda.
Sudanese President Omar Al-Bashir's visit to South Sudan in early January 2014 was supposed to symbolise his support for Kiir's government against Machar - who for so many years had been Sudan's key ally.
Yet, there are real concerns that Sudan might already have reverted to its longstanding tactic of supporting the opposition forces, which are on the lookout for foreign sponsors and conduits for military support in the region.
Last month, the South Sudanese government repeatedly claimed that opposition forces were allowed full use of Sudanese territory to carry out military operations and attacks.
The South Sudanese crisis has enabled Sudan to present itself to the international community as a force for stability.
Yet, it is unlikely that Sudan can withstand the temptation of settling old scores with the greatly weakened South Sudan.
A protracted civil war in South Sudan would be beneficial to Sudan's interests in the short to medium term, as it would prevent the emergence of a stronger and oil-rich state allied to Uganda - thereby allowing Sudan to re-establish its influence over South Sudanese politics.
The tensions between Ethiopia and Eritrea are far more obvious. Since 1998, these states have been involved in a bitter and undisguised 'long game' of undermining each other's security, building opportunistic alliances and fighting cross-border proxy wars.
Ethiopia has consistently avoided direct involvement in the South Sudanese crisis because of wider geopolitical, diplomatic and security considerations.
The state believes that unilateral and partisan military intervention is counter-productive, and would only exacerbate the existing fault-lines in South Sudan.
It has thus strongly asked Uganda to pull out its troops, even if they had entered South Sudan at that government's request.
Ethiopia believes that Uganda's military intervention has created harmful regional dynamics, endangering the mediation efforts of the Intergovernmental Authority for Development (IGAD), of which Uganda is a member. Ethiopia sought instead to play a balanced but highly visible role in these mediation efforts.
The crisis may have presented a political opportunity for Ethiopia to play such a role and to prove itself as a reliable partner of the international community. Yet, the state has a very high stake in this crisis.
Firstly, the crisis has provoked an influx of large numbers of refugees into Ethiopia. It is currently struggling to accommodate the more than 90 000 South Sudanese, who are mostly Nuer, who have crossed into its territory since December 2013.
Secondly, Ethiopia feels that the crisis must be stopped before it becomes an ethnic conflict beyond repair, which would complicate and even sharpen the political divide between the Nuer and Anuak ethnic groups that live in Ethiopia's Gambella region.
This border region, where a Nuer president was appointed in April 2013, has experienced persistent struggles for power between these two ethnic groups.
Thirdly, deteriorating security on Ethiopia's long, porous and politically explosive border with both Sudan and South Sudan poses a direct threat to Ethiopia.
More than any other state in the region, Ethiopia seeks to prevent at all costs the total collapse of the South Sudanese government and a prolonged civil war.
This could in turn lead to the marginal areas of South Sudan being used by Eritrea to infiltrate Ethiopian rebel groups and conduct destabilising activities inside Ethiopia.
Ethiopia is also very concerned that a South Sudan-style crisis could materialise in Sudan and ultimately lead to a full-fledged war between the two states.
It has more than 4 000 troops in the United Nations Interim Security Force for Abyei (UNISFA), which was deployed to prevent a border war between Sudan and South Sudan.
Ethiopia is also actively involved in efforts by the African Union to broker peace talks between South Sudan and Sudan; as well as between Sudan and the SPLM-North, which is part of the SRF.
Since February 2014, unconfirmed reports suggest that Eritrean operatives are covertly providing support to South Sudanese opposition forces.
This would be deeply unsettling to Ethiopia, which sees Eritrea as the principal source of instability in the Horn of Africa for as long as President Isaias Afewerki remains in power.
Such support will probably never be fully corroborated, since it is as secretive as it is sensitive. The disclosure of its true extent would not only threaten its effectiveness, but risk major embarrassment to Eritrea - which vigorously denied these reports.
Yet, considerably isolated from Horn of Africa politics and diplomacy, Eritrea is visibly not enthusiastic about the mediation undertaken by IGAD. Eritrea views IGAD as a tool of Ethiopia's ever-increasing military and economic predominance in the region.
Controlling extensive clandestine networks, Eritrea may thus have risked reaching out to the South Sudanese opposition forces in support of Sudan's interests - and in the hope that fragmentation or a government change could later on cause a spill-over of the violence into Ethiopia.
This would be the simplest and cheapest way to keep Ethiopia entrapped in South Sudan's unrest for many years, as armed factions seek passage through Ethiopia to conduct military operations.
As a result, Ethiopia would eventually lose the political capital that it so carefully expended in the hopelessly uncertain course of mediating the crisis.
Eritrea's priority would be to strategically use resulting dynamics to lift its shakier regional position, and improve its own political vulnerability and economic difficulties.
It is also of great importance for Eritrea to solidify its renewed strategic relationship with Sudan. Both Eritrea and Sudan had officially proclaimed their political support for the South Sudanese government during Al-Bashir's official three-day visit to Eritrea in late January 2014.
However, this visit did nothing to allay the apprehension of their strongest rivals - Uganda and Ethiopia. On the contrary, it essentially confirmed their mutual interest of curbing the greater role that Uganda and Ethiopia play in South Sudan.
All this seems unlikely to Western analysts and diplomats, who hastily argue that the fear of a Sudan-Eritrea 'axis of evil' is misplaced; that there is no compelling evidence to date of Eritrean misdemeanours; and that Eritrea is currently weakened to the extent that it can no longer compete in any way with Ethiopia in South Sudan.
Nonetheless, it fits perfectly into Eritrea's interests to ensure that the South Sudanese crisis would produce losses for Ethiopia and minimise its broader regional influence - especially owing to disagreements with Uganda and Sudan.
- Berouk Mesfin, Senior Researcher, Conflict Prevention and Risk Analysis Division, ISS Addis Ababa