The transitional government, which took power after the army overthrew longtime dictator Omar al-Bashir last year, has been holding talks in neighbouring South Sudan since last October with the four main rebel factions that have yet to lay down their arms.

The deal with the Sudan People's Liberation Movement-North (SPLM-N) covers Blue Nile state and the Nuba mountains of South Kordofan, where the rebels continued fighting after South Sudan won independence in 2011.

In a major breakthrough, it sets out future security arrangements between Khartoum and the SPLM-N, the official SUNA news agency reported on Tuesday.

Measures agreed include a ban on the recruitment of child soldiers and an undertaking not to advance beyond the current lines of control.

The 50-page document, signed on Monday in the South Sudan capital Juba and seen by AFP, said "the two parties have agreed on arrangements for the integration, disarmament, demobilisation and reintegration of fighters of the SPLM-N".

It noted "the revolution and change that took place in Sudan is an exceptional opportunity... to build and develop a professional national army that reflects the diversity of Sudan".

The transitional government led by Prime Minister Abdalla Hamdok has made peacemaking with the SPLM-N and other rebel factions based in Sudan's vast western region of Darfur one of its top priorities.

The rebel groups are largely drawn from non-Arab minority groups that long railed against Arab domination of successive governments in Khartoum.

The talks' chief mediator, Tutkew Gatluak, an adviser to South Sudanese President Salva Kiir, said a comprehensive agreement between the Khartoum government and all four rebel groups would be signed on August 28.