South Sudan's army -- which one U.N. official estimates at about 140,000 strong -- is a massive strain on the budget of the semi-autonomous region, struggling to build a nation from the war ruined but mineral rich south.

"To start the process and then get stuck on the way would be a disaster," the south Sudan Demobilisation, Disarmament and Reintegration (DDR) Commission head Arop Moyak Monytoc said.

"Many know no life but behind a gun. To do demobilization without sustainable reintegration...these people will go violent definitely," he said.

Sudan's north-south war killed some 2 million people and forced another 4 million from their homes before a 2005 peace deal. Under the peace deal the south can vote for independence in 2011.

Soldiers leaving the army will initially get food, household goods and some cash to last six months.

But after that their future is bleak. Jobs are not guaranteed and the United Nations has not agreed to give enough money to help them rejoin society, he added.

The rebel Sudan People's Liberation Army (SPLA) became the south's formal army under the 2005 peace deal, which called for both the northern and southern armies to be cut in size.

Under the deal all other armed groups were to disarm or join either the north or south armies. Tens of thousands of armed southerners opted for the SPLA.

Demobilization in the south is due to start in May with some 25,000 soldiers, including the elderly and disabled, the SPLA's Deputy Chief of Staff Salva Mathok said. He said the soldiers had to be demobilised because their salaries were not planned for in the $500 million annual defence budget.

Mathok said lists of those to be demobilized were unclear and some of the names appeared to have been falsified in the hope of getting payments. New militias were also springing up, apparently with the same aim.

One southerner was arrested this month for handing out grenades and guns. "He was going all over the south recruiting he told us this was his army, that he had 50,000 people," Mathok added.

The southern government is pushing the United Nations to pay soldiers $3,500 each to help rejoin society -- many times the average annual salary -- although Monytoc said the government could pay part of the sum.

Adding to the unease, thousands of the soldiers waiting to be demobilised are from a militia that was formerly hostile to the SPLA and only joined the southern army last June.

"It is very sensitive," Monytoc said.