UN Secretary-General Ban Ki-moon flew in to south Sudan's capital Juba on Tuesday to try to speed implementation of the 2005 peace deal that ended Africa's longest civil war.
Aides said Ban would try to resolve sticking points in the rollout of the Comprehensive Peace Agreement (CPA) that ended over two decades of conflict between the northern government and southern rebels. Ban, on his first visit to Sudan, is also due to visit the war-torn western region of Darfur. He said he had secured a pledge from Sudan's president to allow a Darfur rebel leader to leave the country for medical care.
A senior UN official travelling with Ban told Reuters there were "worrying signals" about the implementation of the north-south peace deal, including delays in the promised pullout of government troops from the south, particularly oil areas.
"There are a number of signs that show there is a need for someone to push the CPA forward," the official said. "Both sides have indicated their commitment to the agreement. But it is important not to let it slip."
About 2,000 people gathered in Juba to welcome Ban, waving banners including several in support of former southern rebels and others demanding the northern Sudanese army quit the south.
The army missed a July 9 deadline to redeploy all its soldiers to the north of Sudan, as set out in the peace deal. Sudanese Oil Minister Ahmed Awad al-Jaz said on Saturday northern troops would be withdrawn from oil fields "gradually".
There were also concerns over delays in implementing a nation-wide census, crucial to democratic elections promised in 2009 and a vote on secession for the south due by 2011.