Aid groups warned on Friday it might be too soon for the U.S. military to scale back its emergency operations for Asia's tsunami victims, while an informal cease-fire between Indonesian troops and rebels appeared to have collapsed, threatening to derail relief efforts.

Following a U.S. announcement on Thursday that American forces would begin immediately transferring responsibility for relief operations to the "appropriate host nations and international organizations," some aid groups expressed concern that the move came too quickly, as tens of thousands of survivors from the Dec. 26 tsunami that struck a dozen nations were still in need of food aid and shelter.

Tallies of the dead from the disaster have varied widely, from about 158,000 to 221,000.

"My gut feeling is that no, the civilian side isn't ready to take over," said Aine Fay, Indonesia director for the Irish aid group Concern (search). "The American military, the military hardware has been so useful."

"I'm a bit taken aback that they're thinking of withdrawing it already," she said.

Speaking in Bangkok, Thailand, the U.N. special coordinator for tsunami relief, Margareta Wahlstrom, said she hoped the military would not leave immediately because the relief operations depend on its "resources and machinery."

She added, however, that, "In a number of weeks to a month the military will be able to phase out and [the operation] be supported by an entirely civilian infrastructure."

More than 11,000 U.S. Navy, Marines, Army, Air Force and Coast Guard personnel backed by 16 U.S. Navy ships are currently involved in providing relief support in the tsunami's aftermath, according to the U.S. Defense Department.

Since the operation began, they have delivered more than 8,600 tons of relief supplies to the affected region.

Indonesian officials said last week that all foreign troops should be out of their country by March 26, but they later backed away from that deadline. On Friday, Indonesian President Susilo Bambang Yudhoyono (search) reiterated that the date was not hard and fast.

Yudhoyono joined worshippers on Islam's holiest day to pray at a mosque in Indonesia's Aceh province and to reflect on the massive earthquake and waves that left anywhere from 110,229 to 166,320 Indonesians dead, according to varying government figures.

"Our tears are overflowing and our hearts are stinging with pain," preacher Syafrudin Miga told Yudhoyono and other worshippers gathered on the Islamic feast day of Eid al-Adha (search) at the 17th century Baituraman mosque.

Meanwhile, Indonesia's military confirmed Friday that it had killed 120 suspected rebels who were interfering in relief efforts in the country's worst-hit Aceh province.

"They are the ones who are trying to disrupt aid work," Indonesian military chief Gen. Endriartono Sutarto said in an interview.

"We cannot allow that to happen," he added. "We have to be able to guarantee that aid workers — foreigners and Indonesians — are safe to do their work."

Separatist rebels and troops in Aceh have been fighting for nearly three decades. Both sides agreed to an informal cease-fire in the aftermath of the tsunami to allow distribution of aid and reassure the thousands of international relief workers there, but the truce now appears under threat.

Rebel spokesman Tengku Jamaica said around 20 guerrillas had been killed, and the 100 others referred to by the military chief were unarmed civilians. He denied that the rebels were targeting aid convoys, and accused the military of abandoning the informal cease-fire.

"Talk of stopping offensive operations is a lie," Jamaica said in a telephone interview.

In Sri Lanka, Norwegian Foreign Minister Jan Petersen, in his role as peace broker between the government and Tamil Tiger (search) rebels, held "very constructive" talks Friday with President Chandrika Kumaratunga (search), presidential spokesman Harim Peiris said.

Petersen and his team of envoys were trying to end disputes between the Tamil Tigers and government troops over distribution of aid to tsunami victims. They planned to meet reclusive insurgent leader Velupillai Prabhakaran (search) on Saturday in the rebel stronghold of Kilinochchi.

Each side accuses the other of obstructing deliveries in eastern Sri Lanka, where lines of control between the two sides are unclear.

In Kobe, Japan, hundreds of delegates at a U.N. conference on disasters put the final touches on a pact Friday expected to express strong support for the world body to create a tsunami alert system and help poor nations gird against cyclones, floods and other natural calamities.

But disputes over the wording of the document underscored differences over just what causes such disasters.

The U.S. delegation, along with officials from Australia and Canada, opposed language in the agreement that points to climate change as a possible trigger for future natural disasters.

Almost four weeks after the disaster, reported deaths by government agencies in the affected countries varied by the tens of thousands. Authorities have repeatedly cautioned that amid the death and destruction, getting an accurate toll is almost impossible.