Egypt and the UAE, seen as the key external players in Sudan's devastating war, disagreed on the role the warring parties -- Sudan's regular army and the paramilitary Rapid Support Forces -- would play in a potential peace process.

According to Egypt's foreign ministry spokesman, the meeting this week in Washington was aimed at charting a path towards negotiations to end the war, which has killed tens of thousands and created the world's largest hunger and displacement crises.

The meeting was cancelled over "an unresolved disagreement" about the final joint statement, an Arab diplomat told AFP, requesting anonymity.

"The UAE inserted a last minute change to include no presence for both the army and the RSF in the future transitional process," the source added, calling the stipulation "totally unacceptable".

Cairo, historically the Sudanese army's closest ally, has repeatedly emphasised the "importance of preserving Sudan's national institutions".

Another source close to the negotiations said "the US circulated a draft that everybody accepted, including the UAE, but Egypt did not accept the part that said that the transitional period should not be controlled by any of the warring parties."

The US then "decided to postpone the meeting to a later date," they told AFP.

The United States under Joe Biden and Saudi Arabia have previously sponsored several unsuccessful rounds of negotiations to end the bloody conflict, which experts say has already spilled over into the surrounding region.

The United Nations has repeatedly warned of outside forces fueling the war in Sudan, which possesses coveted gold deposits -- exports from which are nearly all funnelled to the UAE -- as well as huge amounts of arable land and hundreds of kilometres of Red Sea coastline.

Cairo and Abu Dhabi are close regional allies, but find themselves on opposite sides of the Sudan war.

The UAE has been widely accused of arming the RSF, in violation of a UN arms embargo on Sudan's western Darfur region.

Abu Dhabi has issued repeated denials, despite widespread reports from UN experts, diplomats, US politicians and international organisations.

The war has visited mass atrocities on civilians and torn the country apart. The army is currently in control of the centre, north and east while the RSF seeks to consolidate its hold on the west and south, and recently declared a parallel government in areas it controls.