International experts estimate 200,000 people have died in more than four years of conflict in Darfur and 2.5 million others have fled their homes. Washington calls the violence genocide, a term European governments are reluctant to use.
Khartoum says only 9,000 people have been killed.
PARIS MISSION
Peace talks between Khartoum and rebel groups are expected to take place in Libya on Oct. 27.
U.N. Secretary General Ban Ki-moon called for an end to hostilities as he wrapped up a six-day tour of Sudan, Libya and Chad on Sunday.
"There must be an end to violence and insecurity, a strengthened ceasefire supported by the incoming UNAMID-Hybrid Operation, as well as an improvement in the humanitarian situation," he said.
Ban said the priority now was to persuade as many Darfur rebel groups as possible to attend the Libyan talks.
Riek Machar, the vice president of the semi-autonomous southern Sudan, flew to France late on Sunday with a team of senior politicians to try and persuade one key Darfur rebel leader to attend the negotiations.
Abdel Wahid Mohamed el-Nur, the Paris-based founder of the Sudan Liberation Movement, has so far refused to take part, demanding an end to hostilities in Darfur before talks.
British Foreign Office Minister for Africa, Mark Malloch Brown, who arrived in Khartoum on Monday ahead of a one-day visit to Darfur, told Reuters Britain and France were also pressing Abdel Wahid to attend.
Another rebel leader, Suleiman Jamous, said on Monday he was still waiting to hear when he would be allowed to fly to Kenya for medical treatment, six days after Sudan's president promised he would be allowed to leave.
