If the current sparring escalates, the war that ensues could destabilize East Africa just as the region stands on the cusp of an oil boom that will transform its largely languid economies.
Indeed, the giant oil and natural gas fields that are being discovered all the way south from the Horn of Africa through Uganda, Kenya, the Democratic Republic of Congo to Tanzania and Mozambique, all face the risk of becoming war zones themselves.
Some, like Somalia, already are. The DRC is mired in one of Africa's bloodiest and most intractable wars, mainly over its mineral riches.
Water, too, could become a casus belli. The White Nile joins the Blue Nile at Khartoum, Sudan's capital, and the waters of the 4,000-mile, north-flowing river is a source of conflict between Egypt and the upstream African states like Ethiopia and the two Sudans.
But for now, oil's the primary focus. Neither the Muslim, mainly Arab, north nor the south, which is predominantly Christian-animist, can survive without it. And neither side seems prepared to compromise on sharing it.
Both countries are locked in a deadly embrace that spells trouble for the entire region, where tribal and civil warfare is rife, with conflicts often overlapping and showing little concern for international borders.
The center of the current conflict is the poorly demarcated border between Sudan and South Sudan, where most of both countries' oil production is located.
The south formally became independent July 9, 2011, after the region voted overwhelmingly for secession in a referendum held under a 2005 peace agreement that ended two decades of ferocious civil war.
More than 2 million people died in that conflict, one of the longest in a continent plagued by war. Many of those were from famine.
But independence came without an agreement on border demarcation, division of the oil wealth and other problems.
The oil dispute was heightened by the fact that the landlocked south has no means of exporting its oil except through pipelines that run across the north to the terminal at Port Sudan on the Red Sea.
In November, after months of skirmishing the south, which contains 75 percent of the oil wealth, Khartoum began seizing southern oil at the terminal, supposedly in lieu of unpaid transit fees.
The south retaliated Jan. 22 by cutting off all production. On April 10, southern forces seized the Heglig field north of the disputed border, their first major push into Sudanese territory.
Heglig, in South Kordofan state, produces half of the north's oil output. The Permanent Court of Arbitration in The Hague ruled in 2009 that Heglig lies in the north.
Under international pressure, southern forces withdrew April 20 but the skirmishing has continued, with Sudan's air force -- the south has no combat aircraft -- repeatedly bombing southern targets.
President Omar al-Bashir, Sudan's leader since 1989 who has been charged with war crimes in the conflict-torn Darfur region by the International Criminal Court, has vowed Khartoum will crush the upstart south under President Salva Kiir in his capital of Juba once and for all.
"Heglig isn't the end, it's the beginning," he told his troops in what amounted to a declaration of war. "Our advance will never stop."
These oil fields normally produce around 500,000 barrels a day, so both sides face economic suicide if they continue the face-off and halt production.
"All-out war against … South Sudan might not be in Sudan's best interest," noted regional analyst Ramzy Baroud. "The stakes are too high … and Bashir knows he's running out of options."
Khartoum has already lost "three-quarters of its oil revenue after the secession," Egypt's Al Ahram Weekly observed. "Now it is poised to lose the rest."
As for the south, Baroudi says, its "saber-rattling is not an entirely independent initiative.
"It's most recent territorial transgressions -- the occupation of Heglig followed by a hasty retreat 10 days later -- might have been a calculated move aimed at drawing Sudan into a larger conflict."