A top U.N. official says the African Union is backing away from an agreement to allow the United Nations to take over peacekeeping operations in Darfur. International efforts to intervene in Darfur's civil war are meeting stiff resistance.

U.N. Special envoy for Sudan Jan Pronk Tuesday said Sudan may have succeeded in blocking efforts to transform the African Union peacekeeping force in Darfur into a larger, more effective U.N. mission.

In January, African Union diplomats agreed in principle to hand over the seven-thousand strong A.U. mission in Darfur to the world body. U.N. officials had already begun contingency planning for the transition, but an A.U. meeting this week to finalize the decision was postponed.

Speaking to reporters in New York, Pronk said the A.U. commitment to hand over the mission appears to be unraveling in the face of fierce Sudanese pressure. "The government of Sudan has taken strong position against the transition, and that is new. It seems as if also the African Union is perhaps reconsidering its decision. And Sudan has sent delegations to many countries to plead for its case, that is namely, let the African Union stay, and let the U.N. not come. No transition," he said.

Pronk described the current political situation as a stalemate, and warned that the anti-U.N. climate in Khartoum is heating up strongly as political leaders spread word that the arrival of foreign peacekeepers might create a larger war. "There are threats, warnings, there is talk about al-Qaida. And there is a fear in Khartoum that is being used, of course, that the U.N. transition will be not a U.N. transition but a conspiracy, which will bring Sudan in the same situation as Iraq a couple years ago. Of course that is a feeling that is being manipulated by leaders," he said.

The envoy's comments come days after Sudan's President Omar al-Bashir warned that Darfur would become a graveyard for any military contingent entering the region against Khartoum's will.

Washington's U.N. Ambassador John Bolton Tuesday wrapped up a frustrating month as Security Council president, in which he made little progress in transferring the Darfur peacekeeping mission to U.N. control. Another move by the United States and European countries to impose sanctions against individuals said to be blocking peace efforts in Darfur also ran into fierce opposition in the Council.

Speaking to reporters on the final day in office, Bolton had harsh words for Sudan's leaders. international efforts to intervene in Darfur's civil war are meeting stiff resistance. international efforts to intervene in Darfur's civil war are meeting stiff resistance.

"When the president of a country demonstrates that kind of attitude where he's not apparently concerned with welfare, the lives of his own citizens, it has to give everybody concern. We have tried. We've been working with the government of Sudan, working with the African Union, working with the Arab League, working with NGOs, other concerned countries to find a way to get a U.N. presence in Darfur to stop the genocide. That's our objective. One can only hope the government of Sudan shares the objective that its own citizens should live," he said.

War broke out in the vast region of western Sudan three years ago when black ethnic groups launched a rebellion against the Arab-led government in Khartoum. Tens of thousands of people have been killed, and more than two million have been driven from their homes.

U.N. special envoy Pronk said Tuesday that pro-government militias on camel and horseback, sometimes backed by Sudanese army vehicles, are continuing their campaign of rape and killing in Darfur's villages.