Officials said much of the money would come from domestic oil revenues
International donors will be asked to contribute some $2.5bn at a conference in Norway next month.
The Sudanese government and southern rebels signed a peace deal two months ago to end more than 20 years of civil war which left some 1.5m people dead.
UN officials said the plan for Sudan did not, however cover Darfur, because the government and rebels in the region have not reached a political settlement to the conflict there.
It also would not include the costs of a planned 10,000-strong United Nations peacekeeping operation in the south.