A senior Muslim cleric has been called in to help negotiate the release of two Red Cross workers held captive for three months in Sulu province, one of the negotiators said Wednesday.

Sulu Governor Abdusakur Tan, head of the negotiating team seeking to free the two International Committee of the Red Cross (ICRC) workers, said the region's chief "ulama," or Muslim preacher, would try to convince the Abu Sayyaf extremists to release the hostages.

"This is our last-ditch effort to secure the safe release of the two hostages as peacefully as possible," Tan told a local radio station.

Tan did not identify the cleric.

The two Red Cross workers, Swiss national Andreas Notter and Italian Eugenio Vagni, and a Filipina co-worker were abducted while on a humanitarian mission in Patikul town on January 15.

The Filipina, Mary Jean Lacaba, was released on April 2 but the group is still holding the other two hostages and has warned it could behead one of them unless government forces pulled back from around its hideout.

Tan said the Abu Sayyaf kidnappers were still demanding a troop withdrawal but he stressed the government would not comply with this unless the hostages were first released.

He said the ulama was "trying to establish contact," with the Abu Sayyaf, and warned that he could not say when the talks would bear fruit.

Interior Secretary Ronaldo Puno, meanwhile, said the negotiators are also planning to send a doctor to the Abu Sayyaf's lair in Indanan town to check on the condition of the Italian captive, who is reportedly suffering from hernia.

Puno, who flew to Zamboanga City Wednesday morning, said the Philippine National Police (PNP) will deploy a unit of Special Action Force to Sulu.

The interior secretary is meeting with PNP chief Jesus Verzosa and Armed Forces chief Alexander Yano in Zamboanga City to reassess the hostage crisis.

The Abu Sayyaf have been blamed for the worst terror attacks in Philippine history and have been linked by intelligence agencies to the Al-Qaeda network of Osama bin Laden.

Abu Sayyaf militants have kidnapped several other westerners over the past decade, many of whom, according to the Philippines military, were released after payment of millions of dollars in ransom.

The militants also murdered an American hostage, Guillermo Sobero, in 2001. The following year a second American, Christian missionary Martin Burnham, was killed in a military attack that led to the rescue of his wife, Gracia. With reports from Queenie Casimiro, ABS-CBN Zamboanga and Agence France Presse