A former Taliban member and several influential elders have joined negotiations with the hardline militia to step up pressure for the release of 22 South Korean hostages, an official said Saturday.

A South Korean presidential envoy, Baek Jong-chun, was scheduled to hold talks with Afghan President Hamid Karzai on Saturday, an official from the South Korean Embassy in Kabul said. She spoke on condition of anonymity because of embassy policy.

The Taliban has demanded the release of insurgent prisoners in exchange for the South Koreans, who were captured on July 19. One of the original 23 captives was shot to death on Wednesday.

Purported Taliban spokesman Qari Yousef Ahmadi said the militants hoped Baek would be able to "persuade the Afghan government" to swap imprisoned militants for the captives.

"If they don't release the Taliban prisoners, then the Taliban does not have any option other than to kill the Korean hostages," he said, reiterating an earlier threat.

Abdul Salaam Rocketi, a parliament member who once belonged to the Taliban, has joined the talks, said Shirin Mangal, spokesman for the governor of Ghazni province. A second lawmaker and several respected leaders from the province's Qarabagh area, where the hostage were taken, have also joined, he said.

"Today we are hopeful to get a good result because more and more elders have gathered from Ghazni," said Qarabagh police chief Khwaja Mohammad. "I hope the Taliban will listen to these negotiations now because they are neutral people — elders from around Qarabagh district."

Afghan officials have said they are optimistic the hostages could be freed without further bloodshed despite the Taliban's threat to kill the captives.

Negotiators were struggling with conflicting demands made by the kidnappers, including the release of Taliban prisoners and ransom money.

Local tribal elders and clerics from Qarabagh have been negotiating by telephone with the captors for several days.

The South Koreans, including 18 women, were kidnapped while traveling by bus on the Kabul-Kandahar highway, Afghanistan's main thoroughfare.

Ahmadi said the hostages were being held in small groups in different locations and that some of them were in poor health.

"I don't know if the weather is not good for them, or our food," Ahmadi said. "The women hostages are crying. The men and women are worried about their future."