Little of the $4.5bn pledged a year ago for reconstruction by donors has so far reached the southern Sudanese people.
Little infrastructure exists after decades of conflict in the south
The United Nations envoy in Sudan, Jan Pronk, has told donors in Paris that setting up systems to oversee spending in an area devastated by war took time.
The BBC's Jonah Fisher in Sudan says frustration is growing that Sudan's peace deal has yet to deliver badly needed improvements in basic services.
He says oil revenues are available, but the capacity to deliver remains low.
There are hundreds of millions of dollars in the government's accounts but few new buildings in southern Sudan's capital, Juba.
Major projects to create schools, hospitals and roads have yet to begin and teachers, soldiers and civil servants have not been paid.
The delays are blamed on the slow implementation of the peace deal that ended 21 years of war in the south; the teething problems of the new southern administration and conditions attached to aid to prevent corruption.
At the Paris meeting, the vice-president of Sudan, Salva Kiir, who comes from the south, made a point of asking the donors not to make funding for redevelopment contingent on progress to resolve the three-year conflict in the western region of Darfur
Over that time, some 2m people have been driven from their homes into camps by rape, killing and looting.
On Wednesday, Sudanese politicians met the UN, the United States and the African Union (AU) in Belgium to consider proposals to transform a weak 7,000-strong African peacekeeping force into a full-blown UN peace mission in Darfur.
Sudan is still resisting the idea but the US deputy secretary of state, Robert Zoellick, told journalists at the Paris conference that there were now indications that this opposition was now waning.
"We don't have time to waste," he warned.
However, government ministers have said they oppose the move and thousands of Sudanese protested in Khartoum on Wednesday against any UN deployment chanting: "Down, Down USA."
AU ministers are due to decide on Friday whether to ask the UN to take control of their mission in Darfur