A statement from the United Nations Mission in Sudan (UNMIS) said on Monday Jan Egeland's flight into Sudan was not given authorisation to land on Sunday.
Egeland, the undersecretary-general for humanitarian affairs and emergency relief, had been scheduled to visit southern and western Sudan from Sunday to Thursday to assess relief operations.
Jamal Ibrahim, spokesman for the Sudanese Foreign Ministry, told Al Jazeera: "This was not a prevention but a request for adjournment. Our vision was that the circumstances were not conducive to such a visit.
"Celebrations on the occasion of the birthday of Prophet Mohamed were continuing while Muslims were still infuriated by the cartoons offending the prophet.
"We thought it would be wise to adjourn Egelend's visit to Darfur as the government has nothing to fear or to hide. He could come back to make the visit on the right time.
"You may be aware of the incident involving an attack against a Swedish official in Darfur. Thus, to guarantee his safety, we thought it appropriate to adjourn the visit."
The UN statement said the governor of South Darfur, one of the western states scarred by a three-year civil conflict, had stated his opposition to Egeland's visit.
It also quoted Sudan's representative to the UN in New York as stating that Egeland would not be welcome in Darfur or Khartoum.
On Monday, Egeland told Al Jazeera that the governors of southern and western Darfur said he should not visit the region because they did not want him to see the deteriorating conditions in the region.
Egeland said his safety could have easily been guaranteed, adding that the situation in Darfur will not change in two weeks, and that the Sudanese justifications for adjourning the visit were only a pretext for foiling his mission.
Egeland (L) said the Sudanese
foiled his mission
The Darfur conflict has left 180,000 dead - most from disease and hunger - and displaced another 2 million from their homes.
Sudan's government and rebels in Darfur have made little headway in peace talks in Abuja, Nigeria.
Also on Monday, the Norwegian Refugee Council (NRC) announced that Khartoum had refused to extend the group's mandate.
The non-governmental organisation heads the main refugee camp in Darfur sheltering some 100,000 people.
Jens Mjaugedal, head of the organisation's international division, said the NRC "fears for the security, the lives and the health to the extent that all humanitarian aid destined for 100,000 children and adults will be deprived of management and co-ordination".
"We have not received an explanation why our presence is no longer desired," he added.
Although other NGOs will remain in the camp, NRC's departure will cause co-ordination and supply problems for medicines and food, Mjaugedal said.
The NRC's mandate ends on Tuesday.