Sudan's military bombed an oil field in South Sudan on Tuesday, a South Sudan official said, as a dangerous flare-up in border violence appeared to scuttle plans for a presidential summit between the two countries.
Unity State Minister of Information Gideon Gatpan said Sudan dropped at least three bombs near oil fields in the town of Bentiu. Gatpan said the extent of any damage wasn't immediately known.
The attack comes one day after Sudan and South Sudan clashed in the disputed border town of Jau, prompting Sudan to cancel President Omar al-Bashir's trip to meet with South Sudan President Salva Kiir next week.
South Sudan broke away from Sudan last year, but tensions between the longtime foes have remained high.
Among the unresolved issues is the demarcation of the border and an agreement to share oil revenue. South Sudan earlier this year stopped pumping oil because it said Sudan _ which owns the pipelines the south's oil must travel through _ was stealing its oil.
Despite the increased violence, South Sudan held out hope the presidential meeting could still happen. South Sudan Minister of Information Barnaba Benjamin Marial said the south still expects al-Bashir to attend the meeting next week, saying South Sudan had not received an official cancellation from Khartoum.
Marial said the south believes that "forces of war" in Khartoum were trying to derail the peace process, but not al-Bashir himself. He said the south would not take the bait.
"Our president has said clearly we will not be dragged into a senseless war," Marial said. "We will not be dragged into a conflict with Sudan."
In a statement, the White House urged the two sides to "exert the greatest restraint" and said it is "critical" that they proceed with the presidential summit and other meetings.
"Only through direct contact and negotiations over fundamental issues of security and border management ... can Sudan and South Sudan avoid further fighting, achieve vitally needed economic cooperation, and coexist in peace," the statement said.
The two countries disputed which side was the aggressor in Monday's clash in Jau.
Marial said that Sudanese troops "without any provocation" bombed Jau on Monday afternoon before Sudanese ground forces and militia fighters moved in. Marial said that South Sudan troops repulsed the "invading forces" back to the town of Heglig, Sudan. Marial had no information on troop numbers involved or casualty figures.
Sudanese authorities say South Sudan started the fight.
"These attacks are the responsibility of the SPLA and the South Sudanese government," Sudanese Second Vice President Alhaj Adam Yousif said during an address on Sudanese state television late Monday. "The SPLA attacks have targeted our oil and our army." The SPLA is an acronym for South Sudan's military.
Sudan said that the Darfur-based rebel group Justice and Equality Movement, or JEM, fought alongside the SPLA during Monday's clash.
The border violence continued into Tuesday near Benitu, Gatpan said.
"They are hovering and dropping over the northern part of town in the oil fields, the main Unity oil fields," Gatpan said. He said teams were being sent to the oil fields to assess the damage.
Yousif said that given Monday's violence, the presidential visit to sign agreements recently reached in Ethiopia would not happen.
"The visit of President Bashir was tied to good neighborly relations," said Yousif. "There is no way for this summit to take place now."
The cancellation of the summit effectively halts momentum in negotiations between the two countries on issues leftover from a 2005 peace deal that saw South Sudan separate from Sudan last July.
Oil has been the biggest disagreement. The row prompted South Sudan to shut down its oil production in late January, depriving both countries of a critical revenue stream.
Talks were stalled until two weeks ago when the two sides reached an agreement on citizenship and border demarcation. The agreements _ meant to be signed next Tuesday _ were seen as positive steps.
But there were early signs the deal might not hold. Both countries have accused each other of supporting rebel groups on either side of the border, though both sides deny the allegations.
Sudan's Minister of Defense Abdel-Rahim Mohamed Hussein recently said that any rebel activity in Sudan's South Kordofan state could cancel the agreements. Sudan is battling the rebel SPLM-North, which until South Sudan's secession was linked to the south's ruling party _ the SPLA. The south has said it is not supporting the SPLM-North.
The cancellation of the presidential summit will set north-south relations back, said Aly Verjee, an analyst for the Rift Valley Institute.
"The new fighting unfortunately trumps progress made in recent negotiations. It is unsurprising that talks have been canceled given those events," he said.
Marial said South Sudan is still committed to the presidential summit.
"Our invitation still stands as it is. These are forces within the (ruling) NCP party which don't want this process to continue," he said.
The U.N. refugee agency said Tuesday that it fears for the safety of refugees who have fled the fighting in South Sudan after the violence flared up in recent days. Spokeswoman Melissa Fleming said more than 16,000 people who have fled the Nuba mountains in Sudan are currently living in South Sudan's Yida settlement.
She said the agency wants to move the refugees away from the border where the fighting is taking place.
In total, more than 105,000 Sudanese have fled to South Sudan and 30,000 have fled to Ethiopia.
Associated Press writers Mohamed Osman in Khartoum, Sudan and Frank Jordans in Geneva contributed to this report.