South Sudan President Salva Kiir told the parliament he would not withdraw South Sudanese forces from Heglig, saying that his country had been acting in self-defense after air and ground attacks by Sudan.

Leaders of each side on Thursday accused the other of wanting war.

With much of the region’s oil in South Sudan and the only pipeline to transport it to the coast routed through Sudan, the two countries have been at loggerheads over how to split the oil revenue, how much South Sudan should pay in oil transit fees and how the border should be drawn. Efforts to resolve the differences have all but collapsed, with Sudan withdrawing from the peace talks Wednesday.

The fighting between the two nations was the worst since South Sudan seceded from the north inJuly after an independence referendum. The deepening conflict threatens to dash peace talks to unravel the tangle of disputes between the two neighbors, which engaged in 21 years of civil war ending in 2005.

Sudan, furious about South Sudan's seizure a day earlier of its most important oil field in the town of Heglig, bombed a bridge outside the South Sudan oil town of Bentiu, killing one civilian and wounding four, officials said.

JOHANNESBURG, South Africa –- Sudan and South Sudan teetered dangerously on the edge of war Thursday after South Sudan refused to withdraw its troops from a disputed border area despite calls to do so by the United Nations and African Union.

Kiir also said South Sudanese forces to could take control of the disputed area of Abyei, which is occupied by Sudan, and demanded that the U.N. pressure Sudan to abandon the region. He said he did not want to see the country plunged back into meaningless war but the country should prepare for it if Sudan repudiated the peace talks.

“I always say we will not take the people of South Sudan back to war, but if we are being aggressed like this we will have to defend ourselves,” he said. “I am appealing to the citizens of the Republic of Sudan, especially the mothers, not to allow their children to be dragged into a meaningless war.”

Sudanese President Omar Hassan Ahmed Bashir said war was possible because of decisions made by South Sudan.

“Our brothers in South Sudan have chosen the path of war, implementing plans dictated by foreign parties who supported them during the civil war,” Bashir told reporters. “War is not in the interest of either South Sudan or Sudan but, unfortunately, our brothers in the South are thinking neither of the interests of Sudan or of South Sudan."

Sudan vowed to mobilize its army to swiftly drive South Sudan's forces back, raising the threat of a return to full-scale war.

The African Union and U.N. called on South Sudan to withdraw its troops. U.N. Secretary-General Ban Ki-moon has called for a presidential summit to end hostilities.

Kiir told the parliament there had been several international appeals to him to command his forces to leave Heglig.

“Last night I never slept because of the telephone calls,” said Kiir, who described a call from Ban. “He gave me an order that I’m ordering you to immediately withdraw from Heglig. I said I’m not under your command."

South Sudan's invasion follows several cases of Sudanese war planes bombing South Sudanese oil wells in recent months, as well as bombings of border areas. Fighting between Sudan's forces and rebels loyal to South Sudan has been raging along the border, with Sudan accusing its southern neighbor of arming and supporting the rebels.

Last week South Sudan claimed to have shot down a Sudanese fighter jet after two Sudanese war planes bombed South Sudan's oil fields. Sudan denied the claim.

Both sides have been talking of war for months, as peace talks floundered and the key issues of oil revenue share and drawing the border remained unresolved.

In January, after Sudan commandeered several ships with South Sudanese oil, South Sudan accused it of stealing the south's oil and abruptly turned off its oil production - accounting for 350,000 barrels a day, and equal to more than 95% of South Sudan’s budget revenue. Since then, relations have deteriorated sharply.

The U.S. State Department Wednesday condemned South Sudan's seizure of Heglig, which it said increased tension to a dangerous level. It also condemned Sudan's bombings of South Sudan. Britain and the European Union issued similar condemnations.

In recent months, South Sudan has also accused Sudan of building two secret pipelines to siphon off oil from transit pipelines and steal South Sudan's oil. The first of the pipelines was discovered when South Sudan shut down its oil production in January. The second was found late last month, as South Sudan's forces pushed into the disputed border area between the countries.

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-- Robyn Dixon

Photo: South Sudan's President Salva Kiir addresses the parliament Thursday, April 12, 2012. Credit: Waakhe Wudu / AFP/Getty Images