KABUL, Afghanistan (AP) - Militants threatening to kill three U.N. hostages said they began negotiations on Saturday with Afghan and United Nations officials.

Authorities have not confirmed any contact with the kidnappers, who are demanding a U.N. pullout from Afghanistan and the release of Taliban prisoners. But the U.S. military did say on Saturday that efforts to free the three have reached a "sensitive" stage.

Syed Khaled, a spokesman the Taliban splinter group Jaish-al Muslimeen, said talks began at a secret location in southern Afghanistan, initially through two go-betweens.

He said his group's leader, Akbar Agha, was leading its delegation but that he couldn't name any of his go-betweens.

"The negotiations started one hour ago," Khaled told The Associated Press in a telephone call Saturday afternoon. "If there is a need, there will be face-to-face talks."

Annetta Flanigan of Northern Ireland, Angelito Nayan of the Philippines, and Shqipe Hebibi of Kosovo were snatched from a marked U.N. vehicle in Kabul nine days ago.

The abductions were the first kidnappings of foreigners in Kabul since the Taliban was ousted in 2001. They sparked concern that militants were copying the tactics of their Iraqi counterparts.

The militant group released a videotape of the hostages last weekend to back its claim of responsibility but has offered no proof since of their condition.

Afghan officials doubt the little-known extremist group could have pulled off the kidnappings without the help of a local militia or criminal gang, raising hopes that their release can be negotiated.

On Friday, the militants extended until Saturday night a deadline after which they would decide whether to kill the hostages. The group is also demanding that British troops leave Afghanistan and that the United States release Muslim inmates from Guantanamo Bay, Cuba.

The U.S. military, which has volunteered to help in any rescue, said Saturday it was getting daily government briefings on the situation.

Spokesman Maj. Scott Nelson said he couldn't give details of efforts to free the three "because things are too sensitive now." But he praised Afghan officials for "doing a good job in trying to get a resolution."

"The health of the (election) workers is with the kidnappers," Nelson told a news conference. "They need to make sure they safeguard their health and the best way to do that is to return them safely to the United Nations."

The U.S. military has hopes that they will be freed, Nelson said.

The militants have backed off a series of deadlines to kill the hostages, claiming negotiations were under way. They also have suggested that Nayan, a Philippine diplomat, might be spared because his country has no troops in Afghanistan.

President-elect Hamid Karzai and visiting Italian Deputy Prime Minster Gianfranco Fini on Saturday condemned the hostage-taking.

"We will do our best to solve this issue and to bring back the hostages to their families as soon as possible," Karzai said.