An international force of almost 10,000 could be deployed in southern Sudan by August after last week's peace deal.
After the peace celebrations, the hard work now begins
The head of the United Nations in Sudan says he hopes they will start arriving in March once the UN Security Council approves the mission.
"We are going to propose 9,000 troops, plus military observers, to be spread throughout south Sudan," he said.
Their task will be to monitor a ceasefire, but he did not indicate where troops might come from.
Speaking on his first visit to what is likely to be the new southern capital, Rumbek, Jan Pronk said the challenge to secure peace and develop the south was huge.
The BBC's Jonah Fisher in Rumbek says that only one in five children attends primary school there, and other indicators show it to be one of the poorest places on earth.
The UN has asked for $600m to fund projects this year alone.
Last week the leaders of the northern Arab government signed an agreement with southern rebels to end a bloody 21-year-old civil war.
Mr Pronk has spent much of his recent energies trying to galvanise the world to take action over the violence in the two-year conflict in the western province of Darfur.
The African Union has agreed to deploy up to 4,000 troops there with a limited mandate, but so far only one-third that number have arrived.
They have proved unable to stem the violence which has seen some 2m people displaced.
The UN Security Council has threatened tough sanctions against the government if it fails to stem the violence.