The announcement coincided with reports of continuing violence in Sudan's remote west and growing disillusionment over efforts to push for a settlement in the five-year conflict.

The African Union's Darfur envoy Salim Ahmed Salim, and his UN counterpart Jan Eliasson, told reporters they had just wrapped up an "intense" round of meetings with the main sides in the conflict.

"All that the movements, including the government of Sudan, have said is that they are prepared to discuss security arrangements," said Salim.

"But each one of them had his own position on how this can be brought about ... Whether this could lead to a cessation of hostilities or to a ceasefire, this is the work that is being accomplished now."

Eliasson said he was hoping to persuade all sides to at least reduce current levels of violence to clear the way for the resumption of long-term peace talks before the end of the year.

Current peace efforts had been made "almost impossible", he added, by a surge in banditry and fighting, on top of Sudan's worsening relationship with Chad, which borders Darfur.

Recent months have seen clashes of government and rebel forces in West Darfur and, last week, reports of the looting of North Darfur's capital El Fasher by pro-Khartoum militias. On Thursday, the U.N.'s World Food Programme said it was having to cut food rations to 3 million Darfuris because of attacks by armed bandits on its convoys.

REBEL GROUPS

More than 18 months of joint A.U./U.N. diplomacy has so far failed to secure peace negotiations or even face-to-face meetings between Sudan's government and the bulk of Darfur's fractured rebel groups.

Peace talks in Libya in October ground to a halt after many of Darfur's main insurgents decided to stay away.

UN Secretary General Ban Ki-moon said he was "extremely disappointed at the lack of progress on all fronts" of the conflict. Darfur commentator Alex de Waal this week concluded that: "The international mediation has exhausted its options."

The peace process has been complicated by a series of unsolicited offers of help, most recently from UK Labour peer Lord Ahmed and a separate proposal from UK Prime Minister Gordon Brown to hold peace talks in Britain.

Salim and Eliasson welcomed the offer, even though Britain had not consulted them in advance.

"They have accepted that this effort is going to be under the lead of the United Nations and the African Union," said Eliasson.

International sources in Khartoum said Brown's offer, made on the eve of Global Day for Darfur, surprised many in Britain's diplomatic community, who were not briefed beforehand.

One aid worker, speaking on condition of anonymity, said that any offer to push the peace process forward was welcome. "But this one came out of the blue. No one was consulted and there was no coordination. It seemed very vague and designed to grab headlines."

A spokesman for the British embassy said staff had been briefed "subsequently", after the official announcement.