"It is an important milestone for building good neighbourly relations between the two states," the spokesperson added in a statement. "The Secretary-General is encouraged that the two governments have significantly narrowed their positions on contentious issues." According to media reports, the two countries reached agreement this past weekend on how much South Sudan will pay to transport its crude oil through Sudan's pipelines. South Sudan's oil output had been shutdown earlier this year due to differences over payment rates. In his statement, the spokesperson noted that the Secretary-General, however, regrets that the two sides have not met the 2 August deadline set by the Security Council in endorsing the Roadmap put forward in a communique from the African Union's Peace and Security Council at a ministerial meeting in Addis Ababa, Ethiopia, in April. The Roadmap, for implementation by both Sudan and South Sudan, aims to ease tensions, facilitate the resumption of negotiations on post-secession relations and normalize the relations between the two countries.

"He [Secretary-General Ban] urges the Sudanese and South Sudanese leaders to muster the necessary political will to resolve all outstanding issues," the spokesperson added. South Sudan became independent from Sudan in July last year, six years after the signing of the peace agreement that ended decades of warfare between the north and the south.

However, the peace between the two countries has been threatened over recent months by armed clashes along their common border and outstanding post-independence issues that have yet to be resolved.

In the same statement, the spokesperson said that Secretary-General Ban commends the Government of Sudan and the Sudan People's Liberation Movement-North (SPLM-N) for signing, separately, the so-called Tripartite Memoranda of Understanding - with the African Union, League of Arab States and the United Nations - on humanitarian assistance to war-affected civilians in the Sudanese states of South Kordofan and Blue Nile.

"He [Secretary-General Ban] urges the Government of Sudan to expeditiously enable the delivery of aid to the populations concerned," the spokesperson said.   The two Sudanese states, which lie on the border with South Sudan, have been beset by fighting between Sudanese forces and the SPLM-N since last year.

The SPLM-N was previously part of the rebel movement that fought for the independence of South Sudan. Along with food shortages, the violence has led some 170,000 Sudanese to seek refuge in South Sudan, according to the Office of the UN High Commissioner for Refugees (UNHCR), with more arriving every day.

The impending rainy season and logistics issues have affected the humanitarian response to their plight. Last week, the UN World Food Programme (WFP) announced it plans to air drop lifesaving assistance to displaced persons located in areas which have limited infrastructure.