Abyei in Southern SudanSouth Sudan has issued a new argument to support its claim on a major oil field given to the North as part of the Abyei ruling last week at The Hague. Disputing the North's possession of the oil field, the South says the prized land is still part of a separate southern region.

South Sudan's ruling party, the Sudan Peoples' Liberation Movement, or SPLM, says that the Heglig oil field belongs to the southern Unity State region. The SPLM is threatening to appeal this continued border dispute at The Hague as a separate case.

Southern officials explain their new position by saying that while the Abyei case was ongoing, it was not wise to decide between the alleged separate claims on the oil field between Abyei and Unity State.

But now that it has lost that portion of the ruling, it says it will press a separate claim on the oil field by its Unity region.

The dispute has become so complicated, with both sides pointing to often inaccessible anthropological and historical evidence that is decades and sometimes centuries old, that experts are not able to easily decipher the validity of the two sides' various claims.

Sudanese analyst Fouad Hikmat sees the latest debate over the oil field as political posturing within a fragile peace arrangement that could collapse at any time. According to Hikmat, both sides need to position some claim on the disputed border regions as legitimate in case relations between the North and South deteriorate.

"Everybody is throwing these arguments now for future discussions, future problems. If something goes wrong, then there is an argument. People are preparing something. Everyone is figuring out what does this mean, this decision," Hikmat said.

The Permanent Court of Arbitration ruled in the South's favor by placing most of the disputed area within Abyei borders. But the court gave the North a major victory by excluding the oil fields from the territory. The South had been arguing for a wide demarcation of Abyei's borders because it hopes the territory will vote to join South Sudan in a referendum that is expected to be held on the same day as the January 2011 southern Sudan independence vote.

International observers breathed a sigh of relief as each party immediately accepted the Abyei ruling. But the calm waned as the two sides began trading jabs over the territory.

As the South refuses to cede the disputed oil field, Khartoum angered many southerners by declaring that it is no longer going to share oil revenues from Heglig with the South.

Northern Sudan leader Omar al-Bashir has also drawn complaints from Southern leaders for indicating in a recent speech that non-settled Arab nomads in the Abyei area would be able to vote in the 2011 self-determination vote. The Arab nomads are often associated with northern Sudan, whereas the settled farmers are tied more to the South.