The offer came as spokesmen for the kidnappers said they were "optimistic" about talks aimed at releasing the group of Christian aid workers captured in the southern province of Ghazni and held captive more than three weeks ago.

Kabul has steadfastly rejected previous offers of a prisoner swap and its position was reiterated by President Hamid Karzai's office Saturday.

"We are optimistic about the result of our talks," Qari Bashir, one of two Taliban negotiators, told reporters outside the offices of the Afghan Red Crescent Society in Ghazni, 140km south of Kabul.

But he reiterated: "The hostages will be freed if the government accepts our demands to free some prisoners.

"If they accept our demands, maybe they'll be freed today or tomorrow," he said, speaking during a pause in the talks with South Korean government representatives, at what amounted to the Taliban's first press conference in several years.

The al-Qaeda-backed insurgents, who have been waging an insurgency since being toppled from government in 2001, usually speak to the media through spokesmen who make telephone contact from undisclosed locations.

Taliban negotiators resumed face-to-face talks with a South Korean delegation Ghazni early Saturday after the two sides met late into the night Friday, apparently without breakthrough.

With talks with the Afghan government over the hostages apparently deadlocked, direct negotiations between the rebels and the South Korean team are seen as one of the last hopes for the group.

The hardline rebels have already shot dead two hostages and threatened to murder more.

Seoul has pleaded with Kabul and Washington to do what it can but is powerless to guarantee a prisoner exchange. A government negotiator said last week South Korea could only offer a ransom.

Presidential spokesman Homayun Hamidzada told AFP Saturday he could not reveal details of Kabul's efforts to end the crisis.

But there had been "no change of the position of the Afghan government regarding the release of Taliban prisoners," he said.

President Hamid Karzai's administration came under heavy criticism, notably from Washington, when it freed five important Taliban fighters in exchange for an Italian journalist, whose two Afghan colleagues were beheaded.

The government has been trying to persuade the rebels to free the 16 women in the group on the grounds that it is "un-Islamic" to hold female captives. Other Taliban demands could then be considered, they have said.

The rebel negotiating team is said to be in Ghanzi under a government guarantee that they will not be arrested.

Asked about the condition of the captives, most of whom are reportedly ill, the other Taliban negotiator, Mullah Nasrullah, said: "They're good."

Medicines were delivered to them last week.

The South Korean embassy in Kabul will not comment on the talks. In Seoul, a presidential spokesman said: "For the safety of the hostages, no details of the talks can be released for now."

The 23 South Korean aid workers, 16 of whom are women, were abducted in Ghazni province while travelling on a key highway, which many foreigners consider a no-go area because of a general decline in security.

The Taliban, allied with the al-Qaeda network, are also linked to a militant group holding a German engineer and four Afghans captured in Wardak province near Kabul the day before the South Koreans' abduction.

The militants have demanded a prisoner exchange for the 62-year-old engineer, who was captured with another German who was shot dead days later.

The hardliners were in government between 1996 and 2001, when they were driven out by a US-led coalition for sheltering al-Qaeda -- blamed for the 9/11 attacks that year.