Washington has clearly communicated that peace talks with the warring parties in Saudi Arabia would need to be inclusive, Perriello told reporters, including the United Arab Emirates, Egypt, regional East African bloc IGAD and the African Union.

While the negotiations may or may not start around April 18, and it was unclear whether the warring parties would agree, Perriello said it would be a natural time for talks to resume after the holy month of Ramadan, as well as a donor conference in Paris planned for April 15.

"I'd like the talks to start tomorrow, but I think that realistically we're looking at after Ramadan. But I think in the meantime, we want to use that period between now and the start of talks to be exploring every angle we can that it's teed up for success," Perriello said.

"That would be a good timeline to do it. But it's not firm."

On Sunday, General Yasir al-Atta, one of the army's top leaders, said there would be no negotiations or truce with the RSF.

The army and the paramilitary Rapid Support Forces (RSF) began battling each other in mid-April last year as long-simmering tensions erupted into heavy fighting.

Saudi Arabia and the United States led unsuccessful talks in Jeddah last year to try to reach a truce.

The conflict has created the world's biggest displacement crisis, pushed parts of the 49-million population close to famine, and triggered waves of ethnically driven killings and sexual violence in the western region of Darfur.

Perriello said that the United Arab Emirates - which has been accused of supplying the RSF with military support, a charge the UAE denies - and others in the region are aware the situation is "quickly hurtling out of control and that the RSF is not in a position right now where it's marching to either military or diplomatic victory."