Medicine is delivered for the ill Korean hostages as negotiators try and break the deadlock in the talks with their captors. Afghan doctors delivered medicines on Sunday (August 5) for 21 South Koreans kidnapped by Taliban rebels in Afghanistan more than two weeks ago. The head of a private Afghan clinic said his team had dropped more than $1,200 worth of antibiotics, pain killers, vitamin tablets and heart pills in an area of desert in the Qarabagh district of Ghazni province as instructed by the rebels. "We have given some drugs to be given to the Korean hostages and have also come to know that among the Korean hostages are some doctors and nurses and they know about these drugs and they can use it." Mohammad Hashim Wahaj told reporters in Ghazni, the main town of the province, where 23 South Korean church volunteers were snatched from a bus on July 20. The Taliban have killed two of their captives and are threatening to kill the rest if the Afghan government fails to release rebel prisoners. Kabul has refused to free jailed Taliban, saying that would just encourage more kidnappings. The hostage issue is likely to cast a shadow over two days of security talks between Afghan President Hamid Karzai and U.S. President George W. Bush due to begin at the U.S. presidential retreat, Camp David, later on Sunday. Wahaj said he had been in contact with the kidnappers who told him two of the remaining hostages were seriously ill. The Taliban were willing to free those two hostages, he said, but only if two Taliban prisoners were also freed. "The Taliban side, they told us that the health of two of the hostages is very serious and they are in bad condition and they told me that 'We (Taliban) have told the government of Afghanistan that we (Taliban) are ready to exchange two ill Korean hostages for two Talibs." Wahaj said. The insurgent demand for prisoners to be released has proved a sticking point in all negotiations so far. The South Korean government is under intense domestic pressure to secure the release of the hostages, but Seoul has told the insurgents there is a limit to what it can do as it has no power to free prisoners in Afghan jails. A South Korean delegation was in Ghazni seeking face-to-face talks with the kidnappers to try to break the deadlock. But the Taliban said on Sunday there was no agreement on where to hold direct talks with the Korean diplomats. The Taliban want negotiations in areas they control or with U.N. guarantees for their safety if held elsewhere. An agreement on where to hold the talks was unlikely during the weekend, South Korea's Yonhap news agency said, citing an unnamed government source. The governor of Ghazni accused Pakistani Taliban working with agents of Pakistan's state Inter Service Intelligence (ISI) of holding the captives. The ISI backed the Taliban movement as it rose to take over most of Afghanistan in the mid-1990s, but dropped its support in the wake of the Sept. 11 attacks on the United States in 2001. Afghan officials often accuse the ISI of secretly supporting and harbouring Taliban insurgents. Pakistan denies the charge. A day before the Koreans were seized, Taliban rebels in Wardak province, north of Ghazni, kidnapped two German engineers and five Afghans. One of the Germans suffered a heart attack and was shot dead and one of the Afghans managed to escape. The rest are being held by the Taliban who are demanding Berlin withdraw its 3,000 troops from Afghanistan. Germany refused to do so.