"China officially recognizes the legitimacy of Salva Kiir's government, but Beijing's personal ties to the rebels puts it in a special position," Large told DW.
Ethiopia currently chairs the East African "Intergovernmental Authority on Development" (IGAD) and in this capacity is leading the negotiations between Kiir's and Machar's delegates in Addis Ababa.
Casie Copeland of the ICG points out that cooperation between the SPLM and Ethiopia goes back decades.
However, unlike Uganda, Ethiopia's government is neutral in the present conflict and enjoys the trust of both sides. "It is a good sign that the talks are taking place in Addis Ababa," Copeland told DW.
Economic ties are also strong. Many thousands of Ethiopians moved to South Sudan in past years in search of work. Many of them found themselves caught up in the violence which is increasingly taking on the appearance of an ethnic conflict.
The world's chief superpower has remained largely in the background, apart from a few appeals to both sides.
The US is, however, one of the most vocal supporters of South Sudanese independence. For the time being, it is leaving active mediation work largely to IGAD, Copeland says.
Like other western nations, the US does not question the legitimacy of Kiir's presidency, she told DW.
However Washington is exerting pressure behind the scenes to try and persuade him to be prepared to compromise with the rebels so as to facilitate a peaceful solution to the crisis.
US authority in South Sudan is based less on its economic and military might and more on 'moral considerations,' Copeland says. "Both conflict parties want to present themselves as legitimate and democratic. Recognition by the US plays a big role here."
Copeland considers unrealistic a threat of financial sanctions against South Sudan which is almost entirely dependent on foreign support. "That would hit above all the population which needs help more than ever."