Border clashes between Sudan and its new neighbor to the south, South Sudan, may erupt into a full-blown war if peace negotiations are not re-started soon, warned a spokesman for the South Sudan army.

Philip Aguer of the Sudan People’s Liberation Army (SPLA), the regular army of South Sudan, told Agence France Presse (AFP) that fighting over the disputed border will likely escalate will the expected arrival of some 2,000 more troops from Khartoum in the north.

On Sunday, Aguer said, South Sudanese troops recaptured the city of Jau (which is right on the border), just one day after soldiers from Sudan – the Sudanese armed forces (SAF) had seized SPLA bases there.

They [SAF] are still in the territory of South Sudan,” Aguer told AFP. This is a war situation and if they don’t withdraw, the SPLA will force them out. They [SAF] are regrouping and waiting for more troops from Khartoum.”

He added that the northern army appears to be recruiting young men from South Sudan to fight for them.

There is a brigade coming... The SPLA has been tracking their movements and they left Deleng [a town in South Kordofan], Aguer added.

Nhial Deng Nhial, South Sudan's foreign minister, echoed these same concerns.

Although there have been frequent aerial bombardments of different places in the Republic of South Sudan, we think that Khartoum has raised this offensive to an entirely new level by committing ground forces to cross into the Republic of South Sudan, he told BBC.

We are still very much committed to the principle of dialogue with Khartoum - we are still hopeful that we can pull back from the brink of outright war.

Regarding the contested border, the foreign minister added: Khartoum continues to drag its feet although we are agreed that close to 80 percent of the border is no longer in dispute. This in our mind raises serious suspicions.

On Thursday, officials from both Sudan and South Sudan sparred at the United Nations Security Council in New York over who has the right to Jau.

South Sudan became the world’s newest republic this past July, following decades of civil war that killed some 1.5 million people, after seceding from Sudan. However, both nations continue to argue over where the boundary between them lie -- an area that is rich in oil.

UN peacekeeping chief Herve Ladsous warned the UN Security Council: A return to the negotiating table is absolutely essential to prevent a further descent of the two new countries into war.”