He has helped broker a four-week ceasefire between the government and rebels which has allowed the World Food Programme to make its first food drops in more than a decade.

At the same time, 18,000 aid teams have started a massive campaign to vaccinate up to seven million children in an attempt to eradicate polio.

Rebels from the largely Christian and animist south have been fighting for autonomy from the Muslim-dominated north for more than 18 years.

Destitute

On Wednesday, the WFP dropped 100 tonnes of food aid in the Nuba mountains, part of 2,000 tonnes it plans to deliver in the next few weeks.

Sudan's 18-year war has led to widespread hunger

The United Nations food agency says that 158,000 people have been displaced or left destitute following a recent upsurge in fighting in the Nuba mountains.

The Nuba mountains are in central Sudan but groups there are also fighting the Khartoum government.

Health Minister Ahmed Bilal Osman hopes that the vaccination campaign will rid Sudan of the polio within two or three years.

Mr Danforth was appointed by President George W Bush in September with the goal of bringing peace to Sudan and this week held talks with President Omar el-Bashir during his first visit to Khartoum.

Rebel meeting

He said that he gave himself a year to achieve results or he would ask Mr Bush to replace him.

Mr Danforth plans to go to the Nuba mountains on Thursday.

Danforth wants to achieve results within a year

"We want independent eyes to monitor the situation on the ground in the Nuba mountains," he said.

He is also scheduled to meet leaders of the rebel SPLA.

The US recently extended sanctions against Sudan for its alleged support for international terrorism but correspondents say that relations have improved since the 11 September attacks on New York and Washington.

Khartoum has shared intelligence with US authorities.

Prime suspect Osama Bin Laden used to live in Sudan but left in 1996.