The decision by the Sudan People's Liberation Movement (SPLM) to rejoin the Khartoum government days after pulling out has raised the stakes in the implementation of the southern peace agreement, an analyst said.

"The SPLM withdrawal and return was a case of ringing the alarm bells to attract more international attention," said Mariam Jooma, an analyst at the Pretoria-based Institute for Security Studies. "It has reaffirmed the need to implement the CPA [Comprehensive Peace Agreement]."

However, the decision will raise friction between individual leaders within the SPLM, leading to more tensions between the moderates and hardliners. The removal of some key ministers at this time could also affect the outcome of talks on Darfur due to begin in Libya on 27 October.

The SPLM announced the boycott on 11 October, accusing the north of violating the terms of the 2005 CPA and failing to implement the accord. The decision drew a quick reaction from various quarters, with donors and the UN calling for urgent dialogue to resolve the stalemate.

The move was described by the International Crisis Group (ICG) as "the most dangerous political escalation since the peace deal was signed".

The CPA, signed on 9 January 2005 in the Kenyan capital of Nairobi, ended a 21-year civil war between North and South Sudan.

President Omar el-Bashir moved to defuse the tension, meeting southern leaders in Khartoum on 16 October. He later reshuffled his cabinet, appointing several new faces from the SPLM.

Notable among them was the replacement of Lam Akol as foreign minister by Deng Alor, and the appointments of George Burnig as higher education minister, Mansour Khalid as foreign trade minister, James Kuol Run as minister for humanitarian affairs and Kosti Manibe for investment.

"With a weakened GNU [Government of National Unity], you are unlikely to have substantive discussions in Libya, especially given that the SPLM has been reluctant to fully engage on Darfur," Jooma added.

Even with the reshuffle, a planned meeting between Bashir and SPLM leader President Salva Kiir Mayardit, and a demand by the SPLM that their grievances be addressed by early January, analysts say the dispute over Abyei remains a major sticking point.

The region was granted special administrative status by the CPA and given the option to decide in a referendum in 2011 whether to join the South. The Abyei Boundary Commission ruling was, however, disputed by the ruling National Congress party (NCP), leaving an administrative and political vacuum in a region with a significant percentage of Sudan’s oil reserves.

Bringing peace to the region, according to the ICG, would require addressing national political issues between the NCP and the SPLM, and local ones between the Ngok Dinka and the Misseriya communities.

"The international community needs to re-engage across the board on CPA implementation but nowhere more urgently than Abyei, where the risks of a return to war are rising," the ICG said in a statement on 12 October.

Among other steps, tension in and around Abyei needed to be de-escalated while the role of oil in the impasse and wealth-sharing provisions in the Abyei protocol had to be sorted out.

"More generally, oil is tied directly to the CPA’s viability," the ICG said, noting that revenue from Abyei’s oilfields was estimated at US$599 million in 2005, $670 million in 2006 and about $529 million in 2007. 

"The parties need to open a new, transparent dialogue on oil issues, including a plan to establish a revenue-sharing agreement between North and South beyond 2011," it added.