Sudan has rejected a plea by departing U.N. Secretary-General Kofi Annan for a hybrid U.N.-African Union peacekeeping force in Darfur.

Annan, in a final appearance before the Security Council, urged envoys to keep pressure on Khartoum to accept a blue-helmeted peacekeeping mission.

Sudanese U.N. Ambassador Abdalmahmood Abdalhaleem Wednesday poured cold water on Secretary General Annan's hopes for a diplomatic breakthrough in his last days in office.

Earlier, Mr. Annan briefed the council on a letter he received from Sudanese President Omar Hassan al-Bashir, accepting a three-phase approach for ending the violence in Darfur. The secretary-general said he was encouraged that the three-phase plan would end with deployment of a hybrid U.N.-African Union peacekeeping force in Darfur.

The Security Council has authorized a 22,000-strong blue-helmeted force to replace a badly understaffed 7,000 troops in the A.U. mission.

But Ambassador Abdalhaleem said flatly Sudan would not accept U.N. peacekeepers.

He said 'There is no blue helmet peacekeepers in Darfur. There is support, logistical support staff by the United Nations, wearing their own helmets. But they are not going to engage in peacekeeping activities.'

He said Sudan envisions a hybrid force as being staffed by African Union troops under African command, with U.N. personnel involved only in logistical and technical duties, not peacekeeping.

'It is not a joint force. Let there be no confusion about it. We are not talking about any joint force by the United Nations and the African Union,' he said.

Despite the apparent rejection, Secretary-General Annan remains hopeful. He told reporters he is encouraged by Sudanese President Omar Hassan al-Bashir's response to his three-phase proposal.

Emerging from his final appearance before the council as secretary-general, Mr. Annan admitted most members had been skeptical in light of past disappointments. He said he has advised them to keep up the pressure on Khartoum.

'Obviously, when there have been so many disappointments, it is only natural that there will be some doubts and hesitations,' Annad said. 'And, this is a challenge for the Sudanese government to prove to the international community that it means business; it stands by the letter it has written to me.'

As part of phase one of Mr. Annan's proposal, Sudan has agreed to allow about 100 U.N. military and police advisers into Darfur, possibly within weeks. The United Nations will also provide $21 million worth of equipment to African Union peacekeepers.

War broke out in Darfur nearly four years ago, when rebel groups began fighting the Khartoum government. An estimated 200,000 people have died of war-related causes and more than two million others have been forced to flee their homes.

Human rights and humanitarian groups report violence has increased in recent weeks.