Rival leaders of Sudan and South Sudan are due to meet Friday in the Ethiopian capital to push for progress on stalled economic, oil and security deals that were drafted to ease tension between the former civil war foes.
The meeting between Sudanese President Omar al-Bashir and his Southern counterpart Salva Kiir comes despite accusations from Juba on Thursday that Khartoum had launched aerial and ground attacks inside South Sudan.
Southern army spokesman Philip Aguer said that Sudanese troops had struck inside South Sudan on Wednesday, just as aircraft were bombing the South's remote north Raja region of Western Bahr el-Ghazal state.
"They attacked on Wednesday, and the fighting continued until late in the afternoon," he said, adding that the number of casualties had not been confirmed.
United Nations peacekeepers could not confirm the reports, and the claims could not be independently verified. Sudanese army officials could not be immediately reached.
But South Sudan's Information Minister Barnaba Marial Benjamin said Kiir was still committed to the talks.
"The talks will still take place as planned, we have given our word and we are committed to them," Benjamin told AFP.
"Our chief negotiator Pagan Amum is already in Addis Ababa... This summit is important because we want to ensure the full implementation of the agreements we have already signed."
State owned Sudan News Agency (SUNA), also reported late Thursday that Sudan's Bashir would attend the talks.
"President Bashir will leave tomorrow morning to the Ethiopian capital Addis Ababa for a two-day visit. He will meet with the president of South Sudan, Salva Kiir, to discuss the pending issues and to speed up implementation of the cooperation agreements signed by the two presidents last September," SUNA said.
Previous meetings of the two leaders have been repeatedly delayed or postponed.
However, delegations from both nations have already arrived in Addis Ababa, the seat of the African Union which has mediated repeated rounds of talks.
The accusations of attacks will add to tensions between the presidents, who are meeting for the first summit since they signed security and oil agreements in September that have not been implemented.
Along with a demilitarised border buffer zone, the September pacts allowed for a resumption of South Sudanese oil exports through northern pipelines. They also said border points would be reopened for general trade.
South Sudan separated from Sudan in July 2011 under a peace agreement that ended a 1983-2005 civil war, but key issues including the demarcation of hotly contested border zones remain unresolved.
The future of the disputed Abyei region, a Lebanon-sized area straddling the volatile border, must also be decided.
The two nations came close to all-out war in March and April last year, when their armies fought bitter battles over their disputed frontier.
Khartoum also accuses South Sudan of supporting rebels operating in Sudan, which has been a major obstacle to implementing the agreements.
The South, in turn, says Sudan backs insurgents on its territory, a tactic it used to deadly effect during the two decades of civil war.