Negotiations between Taliban and Korean officials are deadlocked over the 19 hostages the Taliban kidnapped more than a month ago.
The Taliban have already killed 2 of the male hostages and are threatening to kill the rest if the Afghan government does not free jailed rebel prisoners.
After talks last week, the Taliban freed 2 female captives as a gesture of goodwill, but little progress has been made since.
However, Korean negotiators have stressed they have no power to persuade Kabul to free Taliban prisoners and that it is a matter for the Afghan government to decide.
"The Korean delegation has said they are making all efforts to make the American and the Afghan governments agree on the release of Taliban prisoners," said Zabihullah Mujahid, a Taliban spokesman.
Korean negotiators could be reached immediately for comment.
After coming under sharp criticism for freeing jailed Taliban members in return for the release of an Italian journalist, the Afghan government has ruled out any deal.
Mujahid said the U.S. and the Afghan governments were the biggest obstacles to the release of Korean hostages.
He said the Taliban would not release the hostages unless their jailed comrades were also set free.
The Afghan government has said it would use force to free the hostages if talks between the Taliban and Koreans fail. The Taliban have split the hostages into several groups and warned that any such move would put the lives of the captives at risk.
