The United Nations is discussing how to repatriate up to 500,000 Sudanese refugees as hopes rise of a deal to end Africa's longest running war.
Sudan has seen 20 years of war
UN refugee agency head Ruud Lubbers is due to meet rebel leader John Garang.
On Tuesday, Mr Lubbers met President Omar al-Bashir in the capital, Khartoum, to go over the plans.
The UNHCR said the project will be "one of the most challenging in recent times" due to "the near-total collapse of infrastructure in south Sudan".
Peace talks are due to resume at the end of the month.
More than two million people have died in the 20-year war between government forces and Mr Garang's SPLA rebels.
Half a million Sudanese have fled to neighbouring countries - including more than 220,000 to Uganda - and millions more are internally displaced.
But the BBC's Elizabeth Blunt says confidence in Sudan's peace agreement is growing and already people are starting to try to return to their homes.
A convoy of Nile barges is on its way south, packed with around 2,000 southerners going back home from the capital, Khartoum.
If and when this first trickle becomes a flood, the practical problems will be enormous, she says.
The distance is vast and the area lacks communications, roads or any other means of transport.
Many of the returnees, our correspondent says, will have to get themselves back home the same way they left - on their own two feet.