United Nations ? The U.N. war crimes tribunal has been forced to conduct its investigation of atrocities in Darfur outside Sudan because of the danger to potential witnesses, the chief prosecutor said Tuesday.

Darfur’s volatile security situation, resulting from continuing attacks and killings, has made it “impossible to go there to interview witnesses in Darfur itself,” Luis Moreno Ocampo told the U.N. Security Council.

Moreno Ocampo said his investigators have identified witnesses in 17 other countries.

The Security Council referred the Darfur case to the Hague-based International Criminal Court last March in a resolution that required Sudan’s government and all other parties in the conflict to cooperate. Sudan later agreed to set up its own investigation and a Special Court for Darfur.

Moreno Ocampo said the violence in Sudan “represents a serious impediment” to Sudan’s internal investigations. But he expressed confidence that his own investigation could be successfully completed with witnesses outside the country.

“The evaluation is there is no area (in Sudan) in which they could be protected,” he told reporters after the briefing. “That’s why (we are) doing the investigation from outside Sudan, and we will do it.”

After a public briefing, Moreno Ocampo met privately with the Security Council and elaborated on his initial findings.

“What the prosecutor told us was that the nature of the attacks in Darfur demonstrated a degree of coordination, a degree of strategic operation which implied that someone was in command and control of that operation,” said Britain’s U.N. Ambassador Emyr Jones Parry, the current council president.

Moreno Ocampo said in the public briefing that a list of 51 potential suspects named by a U.N. investigative commission remains sealed “and is in no way binding” for his own probe. The commission concluded in January that crimes against humanity had occurred in Darfur.

He said his office would identify people to be prosecuted in coming months.

The Darfur conflict started in 2003 and has claimed the lives of more than 180,000 people, mainly through famine and disease. Several million more have either fled into neighboring Chad or been displaced inside Sudan.

The violence began after rebels took up arms against the Sudanese government amid accusations of repression and unfair distribution of wealth. The government has been accused of supporting Arab nomads known as the Janjaweed, who have been blamed for a campaign of killings, rape and arson. The Sudanese government denies backing the Janjaweed.