A UN deadline for Sudan and South Sudan to resume talks on oil and other critical issues looked likely to pass without action on Wednesday, as South Sudan accused Khartoum of stalling.
The South's lead negotiator, Pagun Amum, told AFP late Tuesday that his country is ready to resume the African Union-led talks.
Sudan withdrew from negotiations after South Sudanese troops occupied the north's main oil region of Heglig on April 10, in a conflict that led to widespread fears of all-out war.
Amum said Juba has sent a letter to the AU mediator, former South African president Thabo Mbeki, saying "we have been ready to resume talks and we are waiting."
Sudan has not reciprocated, Amum said.
"I believe it is because the government of Sudan hasn't been keen to return to talks, which is in violation of the UNSC resolution and the AU roadmap" underlying the UN resolution, he said.
The May 2 United Nations Security Council resolution gave Sudan and South Sudan two weeks -- until May 16 -- to unconditionally resume the talks.
The unanimous resolution sought to avert a "serious threat to international peace and security" caused by the situation along the disputed border between the two countries, after weeks of fighting.
South Sudan's 10-day occupation of Heglig coincided with Sudanese air raids on South Sudanese territory, actions which the UN condemned and called for a ceasefire.
Khartoum's foreign ministry did not respond to AFP's requests for comment about the talks, but it said late Tuesday that Mbeki would likely be in Khartoum this week.
"Mbeki himself is expected in Khartoum tomorrow (Wednesday) or the day after tomorrow to discuss the details of negotiations, like the dates and the agenda," foreign ministry spokesman Al-Obeid Meruh said.
Sudan's President Omar al-Bashir, an accused war criminal, said last week that Sudan "will not negotiate about any issues" unless security matters are resolved first.
Khartoum accuses South Sudan of backing a major insurgency in South Kordofan state, as well as in Blue Nile, and also of working with Justice and Equality Movement (JEM) rebels from Darfur.
The South says it does not back the rebels but suspected JEM fighters were seen alongside its troops during the Heglig occupation. JEM denied involvement.
South Sudan accuses the north of backing insurgents in the South as well.
The UN resolution calls on both sides to halt the practice.
Bashir is wanted by the International Criminal Court for crimes against humanity, war crimes and genocide allegedly committed in Sudan's Darfur region several years ago.