The UN also sought assurances from the warring factions that humanitarian aid would be delivered unhindered, after six lorries carrying supplies to Darfur, a region in the west of Sudan, were looted.
A UN agency in Sudan says it has received credible reports about the existence of at least 13 mass graves in and around the city of El Geneina in the western region of Darfur.
The US said the people of Darfur have suffered insecurity, violence and atrocities for far too long and that now was the time for peaceful resolution to the violence.World News from the BBC
Now, during the beginning stages of the war, the RSF took control of most of the country's capital city of Khartoum, as well as Darfur, and other regions in Western Sudan.
A leader of a Sudanese militia which fought a war in the western Darfur Region in the early 2000s is due to appear at the international criminal court about now.
The United Nations mission in the Darfur region of Sudan says that more than 10,000 people have been displaced amid a flare-up in fighting between government forces and armed rebels.
Sudan's acting Foreign Minister Omer Ismail has told the BBC that his country's army has changed and will protect civilians in Darfur despite fears voiced by local people.
We urge the signatories to lose no further time in agreeing to a cessation of hostilities and modalities for humanitarian access in Darfur and the Two Areas.
Analysis of satellite and social media data shows at least 68 villages in Darfur have been set on fire by militias since the civil war broke out in April.
Such firsthand knowledge is important to shaping future U.S. engagement with the government of Sudan and opposition groups and leaders regarding Darfur.
Witnesses have accused the paramilitary Rapid Support Forces and allied militias of carrying out ethnic killings against non-Arabs in areas they've recently captured in west Darfur.
At least 60 people have been killed in clashes between the Sudanese army and the paramilitary Rapid Support Forces in the capital of South Darfur State.