Sudan has put on hold nine security and economic pacts with South Sudan but remains committed to good relations if the South ends support for rebels.
"We will stop all nine agreements, not only oil," Sudan Information Minister Ahmed Bilal Osman said at a news conference on Sunday.
"We are still committed to have good relations with South Sudan and if they are serious about implementing the nine agreements we can return to co-operate with them."
His comments followed an order on Saturday from President Omar al-Bashir to shut the pipeline carrying South Sudanese crude for export.
Bashir's command came after he warned the South over backing rebels, who, analysts say, humiliated the authorities with recent attacks.
South Sudan's government in Juba denies supporting insurgents in the north, and in turn has accused Khartoum of backing rebels on southern territory.
Osman, along with Sudan's intelligence chief Mohammed Atta, confirmed that the oil shutdown had begun.
Despite that, Osman said that some South Sudanese oil had already reached the Port Sudan export terminal and the South is free to sell it – as long as it pays the fees owed to Khartoum.
After months of intermittent clashes, Sudan and South Sudan agreed in early March to detailed timetables for normalising relations by setting up a border buffer zone and implementing eight other key pacts.
These allowed for a free flow of people and goods across the undemarcated and disputed border, and a resumption of oil flows which South Sudan cut off early last year after accusing Khartoum of theft.
South Sudan separated two years ago with most of the formerly united Sudan's oil production but the export infrastructure remained under northern control.
Last September the two nations agreed to the nine pacts but they did not take effect as Khartoum pushed for guarantees that South Sudan would no longer back the rebels.
In March, Juba and Khartoum finally agreed on detailed timetables to set all the deals in motion. A month later Bashir visited Juba, symbolising the then-easing of tensions.
But Atta told reporters that as recently as last Friday oil tankers destined for the Sudan People's Liberation Movement-North insurgents in South Kordofan state had left the South.
He also alleged that rebels have "training camps" in the South, which he said also provides weapons, ammunition, medical care for wounded, and provides travel documents for rebel leaders.
South Sudan, in comments made ahead of the Khartoum news conference, vowed to co-operate with the north despite its moves to close the pipeline.
"We will continue to implement the terms of the co-operation agreement," South Sudanese Information Minister Barnaba Marial Benjamin told reporters.
However, South Sudan also accused Khartoum of sending troops southwards into disputed border zones and Juba's President Salva Kiir on Sunday held meetings of the country's top security task force.
Juba's army said Sudanese troops had pushed southwards across the demilitarised buffer zone into South Sudan's Upper Nile state.
"It is unacceptable, and the sooner they withdraw the better," South Sudan army spokesperson Philip Aguer told reporters, adding that Juba would complain to United Nations peacekeepers.
In Khartoum, Osman accused the South's army of failing to pull out of six areas along the border, which is monitored by several dozen observers from both countries and the United Nations. – AFP