CAIRO, April 29 (Reuters) - Warring sides in Sudan are more open to negotiations and have accepted the conflict that erupted two weeks ago cannot continue, a U.N. official told Reuters on Saturday, a possible flicker of hope even as fighting continued.

Volker Perthes, U.N. special representative in Sudan, said the sides had nominated representatives for talks which had been suggested for Jeddah, Saudi Arabia, or Juba in South Sudan, though he said there was a practical question over whether they could get there to "actually sit together".

He said no timeline had been set for talks.

The prospects of negotiations between the leaders of the two sides have so far seemed bleak. On Friday, army leader General Abdel Fattah al-Burhan said in an interview he would never sit down with the RSF's "rebel" leader, referring to General Mohamed Hamdan Dagalo, who said he would only talk after the army ceased hostilities.

Hundreds of people have been killed since April 15 when a long-simmering power struggle between the army and the paramilitary Rapid Support Forces (RSF) boiled over into conflict.

Perthes noted that he had told the Security Council both sides thought they could win the conflict, most recently in a briefing a couple of days ago, but he also said attitudes were changing.

"They both think they will win, but they are both sort of more open to negotiations, the word 'negotiations' or 'talks' was not there in their discourse in the first week or so," he said.

While the sides had made statements that the other side had to "surrender or die," Perthes said, they were also saying, "ok we accept ... some form of talks".

"They have both accepted that this war cannot continue," he added.

While the army has conducted daily air strikes and says it has maintained control of vital installations, residents say the RSF has a strong presence on the ground in Khartoum.

Fighting between the forces has damaged electricity, water, and telecommunications infrastructure, and looting has destroyed businesses and homes. Tens of thousands of Sudanese have fled fighting either to other towns or to neighbouring countries.

The immediate task, Perthes said, was to develop a monitoring mechanism for ceasefires, which have been agreed to several times but have failed to stop the fighting.

Jeddah had been offered as a venue for "military-technical" talks while Juba had been offered as part of a regional proposal by East African states for political talks.

Perthes said that signs of the impending conflict had been visible in early April as international and local mediators scrambled to ease tensions, but they had thought a "temporary de-escalation" had been achieved the night before fighting began.