North-South Sudanese talks on the status of the disputed Abyei region have hit a last-minute snag, also threatening a planned humanitarian cease-fire.

A week ago Sudanese President Omar Hassan al-Bashir and southern leader Salva Kiir agreed in principle to demilitarize the oil-rich Abyei region and allow an Ethiopian peacekeeping force into the territory. The deal was meant to be signed at a ceremony Saturday evening.

But the signing was delayed and talks remained stalled on Sunday, as negotiators attempted to fill in the details of the agreement.

Northern and southern Sudan are in talks to settle outstanding issues ahead of Sudan's scheduled July 9 split.

A 72-hour cease-fire designed to allow for the delivery of critically-needed supplies to civilians in Southern Kordofan state — also is threatened by the diplomatic standoff.

Meanwhile, satellite images of the region show that northern Sudanese forces control the border town of Kadugli and that thousands of civilians have fled to temporary shelters near the United Nations peacekeeping base.

The images, taken Friday by the Satellite Sentinel Project, show at least 89 military vehicles — including heavy ammunition transport trucks — that appear capable and ready to move the battle further south.

The north occupied Abyei last month — one of several developments that have raised fears of renewed war in Sudan as the south becomes independent.

South Sudan voted to split from the north in a January referendum. The sides previously fought a 21-year civil war that ended in 2005.