United Nations ? U.N. Secretary-General Ban Ki-moon warned Thursday that a new peacekeeping force for Darfur could fail unless it gets 24 critically needed helicopters and he appealed to all countries for help.

Ban urged U.N. Security Council members to use their influence to turn international concern for Darfur into concrete offers of aircraft.

“While helicopters alone cannot ensure the success of the mission, their absence may well doom it to failure,” he said in a letter to Council members.

With only three weeks left before the 26,000-member U.N.-African Union force is scheduled to start deploying, Ban lamented the U.N.’s failure to get a commitment for even one helicopter.

Ban said he had personally contacted every country with the potential to contribute a helicopter – from industrialized to major developing nations – “to no avail.”