Brussels, Belgium ? World powers pressed the Sudanese government Tuesday to accept a U.N. peacekeeping force in Darfur province to replace overstretched African Union troops who have struggled to protect civilians from rebels and pro-government militias.

Delegates from more than 70 nations at a conference on Sudan were united in calling for the U.N. force, which the Sudanese government is refusing to allow in to replace AU peacekeepers, and a halt to violence in the vast western region.

“This must stop immediately,” U.S. Secretary-General Kofi Annan said, warning that those frustrating peace efforts could face international sanctions.

The daylong conference in Brussels raised $200 million in fresh donations to support the 7,300-member AU force in Darfur – about half what the AU says it needs to keep the mission running until the end of the year, when the U.N. hopes to take over peacekeeping.