"A high level delegation led by the vice resident, Riek Machar, has gone to Khartoum," said Mangar Amerdid, a spokesman in the office of the southern president.

"It is aimed as an effort to normalise and ease tensions, and to improve the situation in Abyei," he added, but could not confirm who the southern team would meet in the north.

"This is an important mission on a very important matter, and we are hoping for a good reception," he said.

Khartoum's chief Abyei negotiator Al-Dirdiri Mohammed Ahmed said on Friday that the northern government was "open" to negotiations with the south.
Thousands have been displaced by the fighting.

A southern Sudanese minister said more than 150,000 people have fled violence ravaging the border region and surrounding areas since May 21 when northern troops and tanks took control.

However, the United Nations says it can only confirm that up to 40,000 people are displaced.

Abyei's future is the most sensitive of a raft of issues that the two sides had been struggling to reach agreement on before the south's full independence in July.