Sudan seeks good relations with newly independent South Sudan, President Omar al-Bashir told an Arab summit on Thursday, after border clashes this week sparked international alarm.

"We are committed to go forward in resolving these pending issues with our southern neighbours, through understanding, to reach good relations," Bashir told the Baghdad gathering, which opened with a call for peace from UN chief Ban Ki-moon.

Bashir noted that Arab leaders had been following events on the southern border.

"The enemies of peace were pushing South Sudan to attack", he said.

Each side accused the other of starting the fighting which began on Monday.

It was the worst violence since South Sudan declared independence from Khartoum in July last year following an overwhelming vote after Africa's longest war.

Officials in South Sudan's Unity state said the border was calm on Thursday, although northern warplanes were reported to be still flying over the state.

The African Union, UN Security Council and European Union have all called for an end to the fighting.

US Secretary of State Hillary Clinton accused Khartoum of bearing the most responsibility for the renewed hostilities.

Sudan and South Sudan vowed Wednesday to step back from the brink of all-out war after growing international alarm at the violence that included air strikes and tank battles.

AU-led talks in the Ethiopian capital, planned for Thursday, were likely to be deferred as the chief mediator, former South African president Thabo Mbeki, could only reach Addis Ababa on Saturday, South Sudan's top negotiator told AFP.

"We are coming to Addis today, and we have received a message that maybe the meeting will be postponed," Pagan Amum told AFP by telephone, adding he was hoping the talks would start on Saturday.

Amum has said his aim was to "pursue peace" and to stop the recent violence from "spreading to a full fledged war."

Sudanese foreign affairs official Rahamatalla Mohamed Osman was already in Addis Ababa and stressed Khartoum did not want a war with the South.

Analysts said there are elements in Khartoum, as well as the South, opposed to recent moves towards warmer relations between the two countries and suggested the latest flare-up was an effort to sabotage a rapprochement.

But the analysts said they were still hopeful the sides can reach agreement.

Border tensions have mounted since South Sudan's separation.

Earlier in March, after months of failed negotiations, an escalating row over oil fees and mutual accusations of backing rebels on each other's territory, Amum said relations had improved.

He and a South Sudanese delegation visited Khartoum last week to invite their "brother" Bashir to an April 3 summit in the southern capital Juba, and said he had accepted.

But after Monday's fighting Khartoum said it had suspended the meeting.

Bashir is attending the Arab summit despite being wanted by the Hague-based International Criminal Court.

Iraq is not a signatory to the ICC's founding Rome Statute, according to a copy of the treaty posted on the UN's website.

The Iraqi foreign ministry has said on its website that "the protection of President al-Bashir is guaranteed one hundred percent," adding that the same applied to all summit participants.

ICC issued an arrest warrant for Bashir in 2009 for alleged crimes against humanity and war crimes committed in Darfur, the country's western region. A later warrant added genocide to the charges.