The Archbishop of Canterbury has arrived in Sudan at the start of a week-long pre-Lent visit.
Dr Williams marks the beginning of Lent with his visit
During his stay, Dr Rowan Williams is expected to meet Muslim and Christian leaders and hold services throughout the country.
Sudan emerged a year ago from two decades of conflict between the Muslim north and Christian rebels in the south with the signing of a peace agreement.
Dr Williams hopes to encourage all agencies to "strengthen peace" there.
A separate continues to rage in the western region of Darfur. Some 2m people have fled their homes and at least 180,000 have been killed.
His first stop on Sunday will be a visit to shanty town al-Gariya, in the capital, Khartoum, whose inhabitants have been displaced by war.
BBC correspondent Jonah Fisher said those people were just a small percentage of the 2m southerners who squat around the capital, treated as second-class citizens by many of their northern neighbours.
After his al-Gariya visit, thousand of Khartoum's Christians are then expected to join Dr Williams for a service of welcome on Sunday afternoon.
As head of the Anglican Communion, the Archbishop is religious leader of more than 3m southern Sudanese and most of his trip will be spent in the south.
Former Archbishop of Canterbury Lord Carey visited the Sudan three times.
Dr Williams said he looked forward to visiting the Sudanese people "at this crucial time in their country's history" and, in particular, supporting the work of the World Food programme in the country.
"I am anxious to see governments, UN agencies and faith-based organisations working together to strengthen all the moves for peace in a land that has known far too much of war," he added.
Dr Williams, who was invited by the Anglican Archbishop of Sudan, Dr Joseph Marona, will also consecrate a new cathedral in Renk and plans to visit a rural school in an area recently attacked by militia.
The Archbishop's other plans for the visit include holding a service in new southern capital Juba and taking part in food distribution projects in Malakal, capital of the Upper Nile region.