The government of Sudan is demanding that rebel forces leave a strategic town which they captured earlier this week. But rebels have said that it was a legitimate target. The dispute is raising doubts about chances for success at Sudanese peace talks scheduled Monday in the Kenyan capital.

A senior official at the Sudanese embassy in Nairobi, Mohamed Dirdeiry, said the town of Kapoeta had been declared a zone of tranquillity for six months in order for cattle to be vaccinated against the disease rinderpest.

He said this was part of an agreement made with U.S. special envoy John Danforth last December.

Mr. Dirdeiry said the seizure of the town by the rebel Southern People's Liberation Army on Sunday was a violation of this agreement. And he said Sudan wants the rebels to give Kapoeta back.

"We feel that because the rebel movement has taken undue advantage of the tranquillity period and has made that attack, the rebel movement should relinquish that town. That is the least which we can accept. And we think the United States is having the muscle to compel them to do so, if it really feels that living up to the commitments of the parties is something very important to them as a mediator," Mr. Dirdeiry said.

The SPLA spokesman in Nairobi, Samson Kwaje, has denied there was any such agreement. He said such requests for animal vaccinations are normally made in writing by the United Nations, and that the United Nations has not asked to carry out any vaccinations in the area since it was refused permission by the government last November.

With both sides trading accusations, there appears little chance of progress at peace talks due to start in Nairobi on Monday. Negotiations are being organized by the Inter-Governmental Authority on Development, IGAD, a regional body.

Mr. Dirdeiry said the government of Sudan has already lost faith in IGAD. "The IGAD peace process started in the year 1993 and it made very little progress throughout those previous years. And for that reason we are very skeptical about this peace process and we feel that it has been given a lot of time. This forthcoming session is a do or die session for the IGAD. And if it is not going to achieve any progress, everybody will reconsider his agenda about it. If the forum for mediation which we are right now having has proved to be useless, this means that we have to hammer out a new forum for mediation," he said.

The IGAD peace process has hit a stalemate. Sudan's government insists on maintaining national unity. The rebels want self-determination for the south and a separation of religion and state.

An estimated two million people have died in Sudan's 19-year civil war.