The Afghan government and Taliban kidnappers sought on Saturday to find a venue for negotiations to try to free 21 South Korean hostages held for more than two weeks, the provincial police chief said.
A South Korean delegation was in Ghazni province, southwest of Kabul, where the Christian church volunteers were snatched, seeking direct talks with the kidnappers.
But Seoul has told the insurgents there is a limit to what it can do since it has no power to concede the main Taliban demand for the release of rebel prisoners in Afghan jails.
"The venue has not been chosen for talks. Talks are going on to find an agreement on location," Ghazni police chief Ali Shah Ahmadzai told reporters.
"We are in favour of dialogue, that's what logic requires. If that doesn't work, then force may be used," he said. "If the Taliban do not accept dialogue that means they do not want this issue to be resolved peacefully."
The Taliban preferred to hold the negotiations in an area they control, and vouched for the safety of the Korean delegates, a Taliban spokesman said on Friday. Otherwise, the insurgents needed United Nations security guarantees should the Koreans want negotiations to take place outside Taliban-controlled areas.
Police chief Ahmadzai said authorities had managed to send medicines to the 18 women and three men held by the Taliban in small groups at different locations in Ghazni province.
But the Taliban had rejected a request from a group of private Afghan doctors to visit the captives, Ahmadzai said.
The Taliban have said two of the women are seriously ill.
The kidnappers have killed two of their male hostages, accusing the Afghan government of failing to negotiate in good faith and ignoring their demand to release rebel prisoners.
Afghan officials have refused to free Taliban prisoners, saying that would only encourage more kidnappings.
South Korea has appealed to the United States, which has more than 20,000 troops in Afghanistan, to help free the hostages. Washington has said it will do what it can, but has ruled out making concessions to those it considers "terrorists".
A German engineer and four Afghans kidnapped a day before the Koreans are still being held by the Taliban, who are demanding Germany withdraw its 3,000 troops from Afghanistan. Berlin flatly rejected the demand. One German seized with the group was later found shot dead.