Douglas Johnson literally wrote the book on the "The Root Causes of Sudan's Civil Wars," which is considered to be the most authoritative account.
Writing about Abyei, in May last year, he said;
The international community — particularly the United Nations and the United States — have been spectacularly ineffective in getting the Sudanese government to honor its own agreements.
To prevent the Abyei crisis from igniting other conflicts, the international community must stop pretending that both sides are equally at fault. Carrots haven’t worked. Washington will need to wield sticks, such as canceling debt relief talks or suspending normalization of diplomatic relations, if Sudan does not withdraw its forces quickly. But ultimately, Washington has limited leverage over the Sudanese government, having reduced both its diplomatic and economic ties during the civil war.
The key player will be China.There was a time though when Washington did have leverage over the Sudanese government, which it used to help broker the 2005 Comprehensive Peace Agreement.
In early 2002 Khartoum was frightened of being bombed by the U.S. It had been bombed once before, and with its past support for Osama bin Laden, world opinion was against it [Douglas Johnson, again].Just saying.