The discussions, lead by the African Union, are working to end a flareup of hostilities in Ethiopia's northern Tigray region in a conflict blamed for tens of thousands of deaths, and for creating starvation.
Ebba Kalondo, spokeswoman for AU Commission chair Moussa Faki Mahamat, said in a message to AFP that "there was no date limitation put on the talks".
A diplomat with knowledge of the discussions confirmed to AFP that the talks were continuing on Monday, without giving further details, adding: "They are very strict about confidentiality."
A source close to the Tigrayan delegation in South Africa had told AFP at the weekend that the talks would likely continue until Tuesday.
While both parties to the talks have not made comments about the talks, observers say their continuation shows at least a willingness to continue engagement.
In an interview with Chinese state media, Prime Minister Abiy Ahmed voiced hope that peace could be achieved, without making any direct reference to the talks underway in Pretoria.
"We're working towards peace, we are trying to convince the TPLF (Tigray People's Liberation Front) to respect the law of the land, to respect the constitution and to act as one state in Ethiopia," Abiy told the English-language CGTN news channel in an undated interview posted on Twitter.
"Ethiopians should understand, we can solve our own issue by ourselves. And instead of listening from afar, better to respect our own law, better to respect our own culture, better to respect our own (customs)," he said.
"If we could do that, peace is achievable. I hope we'll achieve that."
However, since the negotiations began, intense fighting has continued unabated in Tigray, where government troops backed by the Eritrean army and regional forces have been waging artillery bombardments and air strikes, capturing a string of towns from the rebels.
The violence, which resumed some two years ago, has also exacerbated shortages of food and medical supplies in Tigray, whose officials blame Addis for exerting a blockade preventing relief from reaching people there.
UN children's agency UNICEF said in a report issued at the weekend that about 574,000 people alone had been displaced in Tigray as well as the neighbouring regions of Afar and Amhara since combat resumed in late August.
"Insecurity and restrictions on the movement of aid continue to constrain the humanitarian response across the three regions," it said.
One actor in the conflict, neighboring Eritrea, is not involved in the Pretoria talks despite its forces fighting alongside Ethiopian troops in Tigray.
It is also uncertain, according to talk-watchers, whether Eritrea will respect any hostility-ending agreement that might be reached in these discussions.
Last week, Amnesty International said every party involved in the war had committed crimes against humanity.
"Documented violations of human rights violations... (include) rapes, sexual violence... lootings, torture and extrajudicial killings," Fisseha Tekle, an Amnesty specialist on Ethiopia and Eritrea, told a press conference in Nairobi.
This report was compiled using information from ABC News, Associated Press, and Agence France Presse.