Dan Nolan, Al Jazeera's correspondent in Kabul, said the Taliban had told him that transportation problems in getting the hostages to the release site were delaying the handover.
Qari Yousef Ahmadi, a Taliban spokesman, said on Sunday: "The time hasn't been decided. It could be today."
Meanwhile, Yonhap, South Korea's news agency, said on Sunday that the Taliban had decided not to free any of the hostages, citing a spokesman for the movement.
Neither Afghan nor South Korean officials have confirmed that any hostages are to be released.
At a news conference on Saturday, Ahmadi had said: "Our leadership council decided to free unconditionally and as a gesture of goodwill two women hostages who are sick."