The Sudanese military, together with government-backed militias, is committing acts of "inexplicable terror" against civilians, including children, in Darfur, the UN's top humanitarian official said.
The accusations by Jan Egeland, UN undersecretary-general for humanitarian affairs, came as Sudanese officials indicated they might backtrack from a deal for a mixed UN and African peacekeeping force.
Egeland said spiraling violence in the conflict-wracked region of western Sudan is reaching its worst level since fighting erupted more than three years ago.
"The government and its militias are conducting inexplicable terror against civilians," he told reporters on Saturday in an interview just after returning from his final trip to the area before the end of his term next month.
"The government is arming Arab militias more than ever before ... the angst is that we may be reverting to the same level of violence" as in 2003 when the war in Darfur erupted, he said.
More than 200,000 people have been killed and 2.5 million displaced since rebels from ethnic African tribes rose up against the Arab-led central government in the vast arid area of western Sudan. Khartoum is accused of using the janjaweed militias of Arab nomads to retaliate but the government denies backing or arming the janjaweed.
While in Darfur, Egeland visited a government hospital in Geneina where survivors were being given treatment after an attack last week by government forces and militias that killed 30 people.
"I saw a two-year-old girl who was shot in the neck at point blank by a janjaweed," Egeland said. "This is an act of terror."
The baby's mother and several eyewitnesses confirmed the attack was jointly conducted by the army and militias, he said.
"Those who continue to attack defenseless civilians will be judged," Egeland told reporters at a separate news conference. "There will be a time of reckoning."
UN Secretary-General Kofi Annan announced on Thursday night a multilateral agreement -- reached in a gathering of African, Arab, European and UN leaders in the Ethiopian capital of Addis Ababa -- which could provide for a mixed UN and African Union (AU) peacekeeping mission for Darfur.
But Sudanese Foreign Minister Lam Akol played down the scope of the agreement. Khartoum has not committed to a "mixed force," he said.
"What was agreed upon is a mixed operation," he said.
"The role of the United Nations will be to provide support units and technical assistance to the African mission," Akol said to reporters. "There is no way the main fighting force would be a mixed one."
Sudanese President Omar al-Bashir has firmly opposed any deployment of UN troops in Darfur to replace the 7,000 ill-equipped and poorly funded AU peacekeepers who have been unable to stop the bloodshed.
But other officials have said a combined force would not pose a problem, provided that its leadership and the bulk of its troops were African -- a sign that the Sudanese political leadership may be sending mixed messages in order to avoid the appearance of a policy shift in the face of Western pressure.
Still Egeland said he was confident all parties involved would soon reach a final agreement for a beefed-up force.
"I have no reason to disbelieve the sincerity of the Sudanese negotiators in Addis," he told reporters, adding that he hoped time would not be wasted "wrangling on words."