ABOARD AIR FORCE ONE: The White House called on Sudan on Tuesday to stop its bombing raids of newly independent South Sudan and said the neighboring countries needed to return to the negotiating table to avoid escalation.

“We strongly condemn Sudan's military incursion into South Sudan. Sudan must immediately halt the aerial and artillery bombardment in South Sudan by the Sudan armed forces,” White House spokesman Jay Carney told reporters on Air Force One.

“Both governments must agree to an immediate, unconditional cessation of hostilities and recommit to negotiations,” he said.

Weeks of cross-border fighting between the former civil war foes have raised the possibility of full-blown conflict in a region with one of the most significant oil reserves in Africa.

South Sudan became independent last July under a peace deal that broke up what was Africa's largest country.

But Sudan and South Sudan have yet to settle a long list of disputes, including the position of their shared border and how much the landlocked South should pay in oil transit fees to Sudan.