The Sudan People's Liberation Movement-North, a rebel group in the states of Blue Nile and South Kordofan, said on Wednesday it was ceasing all hostilities until July 31 as a "goodwill gesture" after the overthrow of president Omar al-Bashir.
In a statement conveyed to Reuters in Khartoum, SPLM-N leader Abdelaziz Adam al-Helew said the move was to "give an opportunity for the immediate and smooth handover of power to civilians".
Sudan's military deposed Bashir, in power for three decades, on April 11 and announced a Transitional Military Council would rule for up to two years then hold elections. Protesters have called for an immediate handover of power to civilians.
The SPLM-N splintered from the Sudan People's Liberation Movement that fought for South Sudan's independence, achieved in 2011, and then continued an insurgency against Bashir in the two southern states that remained within Sudan.
The SPLM-N had sought to topple Bashir and is seeking autonomy for Blue Nile and South Kordofan and a redistribution of wealth and political powers in the country.
SPLM-N has several thousand fighters, tanks and other heavy weapons, and is by far Sudan's largest rebel group. It has a presence in Blue Nile and controls large swathes of territory in South Kordofan, especially in the Nuba Mountains area.