JOLO, Philippines (AP) _ Government troop movements prevented Muslim rebels from replying Thursday to a request to free two ailing Europeans being held hostage with 19 others in a southern Philippine jungle, negotiators said.

Negotiators had asked that the rebels release a Frenchman with a urinary tract infection and a German woman, whose family said she had suffered two strokes.

The Abu Sayyaf rebels promised to deliver their response Thursday, but apparently were spooked by the military activity, presidential adviser Robert Aventajado said.

The troop movements _ part of a general withdrawal from around the rebel camp to improve the chances for negotiation _ occurred because the military had not been informed of the planned meeting with the rebels, Aventajado said.

Negotiators expected the rebels to present specific demands soon. But what little trust may have been established in a meeting Wednesday at the rebels' mountain hide-out appeared frail after the Abu Sayyaf skipped Thursday's appointment.

One negotiator, Islamic cleric Ibrahim Ghazali, said the military activity had undercut his assurances to the rebels, and he was leaving the team.

In Wednesday's discussions, the rebels said they wanted to be reimbursed for what it cost them to grab and hold their hostages in a pen in the jungle, a negotiator said Thursday on condition of anonymity.

The Abu Sayyaf did not specify a figure for expenses, which included renting horses, purchasing food and hiring guards. But the negotiator said the two sides might agree on up to $1,700 a hostage.

The Philippine government has a no-ransom policy, which it often sidesteps by paying for ``food and lodging.''

The hostages _ three Germans, two French, two South Africans, two Finns, a Lebanese, nine Malaysians and two Filipinos _ were kidnapped April 23 from Malaysia's Sipadan Island and taken to Jolo, an island in the southern Philippines.

They are being held by the Abu Sayyaf in an outdoor cage made of branches. The Abu Sayyaf, the smaller and more extreme of two Muslim rebel groups active here, are also holding a group of Filipino hostages in nearby Basilan province. They seized those hostages, many of whom are children, on March 20 from two schools.

The Abu Sayyaf's original plan before the April 23 ambush had been to snatch about 100 foreigners, including many Americans. But time ran short, so they just seized a small group and fled, a rebel leader, Abu Escobar told The Associated Press. An American couple in the group managed to get away.

The operation was meant to relieve military pressure on the Basilan guerrillas, he said.

Libya's envoy to the rebels, Abdul Rajab Azzarouq, said the rebels wanted independence for the region, the establishment of Islamic law, and a ban on foreign fishing boats.

``They would like to be given a chance to represent the aspirations of the Muslims,'' said Azzarouq, a former ambassador to the Philippines with extensive contacts in the impoverished region. ``They want development, and they want to do it themselves, to their own way of life.''