KANDAHAR, Afghanistan • Taleban militants holding 19 South Koreans hostage yesterday signalled growing impatience with negotiations as sources close to the talks said they had turned down a cash ransom.

The kidnappers accused Korean hostage negotiators of not doing enough to persuade the Afghan government to accept their demands to release Taleban prisoners.

"The Korean nation must understand that if their hostages are harmed their government will be responsible, because it doesn't do much to gain their release," a purported Taleban statement said.

"Their efforts are not sufficient," according to the statement, read over the telephone to AFP by a Taleban spokesman, Zabihullah Mujahed.

He said the South Korean hostage negotiators had pleaded for more time during a telephone conversation with the Taleban yesterday.

"Our negotiating team were in telephone contact with the South Korean delegation today (Monday). The Koreans are asking for more time," he said. "The Koreans are telling us that 'we're trying to persuade the Kabul administration and the US government to accept the Taleban demands'-but it seems they can't," he added.

The Taleban, who have threatened to kill the remaining hostages if their demands are not met, have not set a deadline, he said.

An Afghan source involved in mediation between the two sides said earlier the South Koreans had yesterday sent a delegation of tribal chiefs to plead their case with the Taleban.

"The Koreans sent a delegation to the Taleban to ask them what they want, other than a prisoner exchange," the source told AFP, asking not to be named because of the sensitivity of the issue.

The US-backed government of President Hamid Karzai has repeatedly refused to bow to the Taleban demand. Washington has also come out strongly against a prisoner swap.

"The Koreans' message to the Taleban is 'we can't help free your prisoners. (Do you have) any other demand?" the source said.

The kidnappers have refused a cash ransom, he said, but refused to give details.