ZAMBOANGA - Philippine authorities said Sunday they were stepping up their crackdown on the Abu Sayyaf bandit group holding two foreign Red Cross workers hostage despite renewed threats to behead them.

National Defense Secretary Gilberto Teodoro Jr. rejected demands by the Abu Sayyaf for a withdrawal of military forces even after a Red Cross official warned that the two hostages, Italian Eugenio Vagni, 62, and Swiss Andreas Notter, 38, could be beheaded.

Sulu Gov. Abdusakur Tan, head of the negotiating team for the hostages, said "we will continue our crackdown on suspected supporters of the Abu Sayyaf, those who give them aid. We will file charges against them."

Tan, who is governor of Sulu province, where the hostages are being held, also rejected the demand for security forces to pull out, saying "we will not move from our locations."

The Abu Sayyaf, who are holding the two Europeans in Jolo, could behead one of them unless the government withdrew all security forces from most of the island, said Philippine Red Cross chief Sen. Richard Gordon.

He told reporters that President Arroyo herself should order the withdrawal, hinting that he would hold her responsible for what happens.

Teodoro, however, opposed this, saying "Senator Gordon's latest statements only serve to strengthen the hand of the kidnappers."

He called for a halt to these "destructive attempts" to interfere in the role of the official negotiating team.

Presidential spokesman Secretary Cerge Remonde said that the government "will do everything it can to ensure the safety of the hostages... without subverting our sovereignty."

He also urged all parties to leave it to Tan and his special committee to handle the talks.

Notter, Vagni and a Filipina Red Cross worker Mary Jane Lacaba were seized while on a humanitarian mission in Jolo on January 15. The kidnappers had previously threatened to behead one of them unless military forces pulled back by March 31.

However, the kidnappers released Lacaba Thursday into the custody of a government emissary.

Government officials, who initially withdrew soldiers and police from around the Abu Sayyaf hideout, have reimposed a cordon around the kidnappers and have brought in 23 village officials and policemen suspected of colluding with them.

Tan said some of these suspects had been brought from Jolo to the port city of Zamboanga for formal investigation, adding that more would be "invited for questioning."

The Abu Sayyaf has been blamed for some of the Philippines' worst terror attacks and has been linked by intelligence agencies to Osama bin Laden's Al Qaeda terror network.

Abu Sayyaf militants have kidnapped numerous Filipinos and foreigners over the past decade. Many of them were ransomed off but some, including two Americans, died in Abu Sayyaf captivity.