MANILA -- United States troops will soon begin to wind down their mission in the southern Philippines, with little sign to date they are any closer to rescuing two American missionaries who begin on Monday their second year as hostages of Abu Sayyaf guerrillas.

Martin and Gracia Burnham are both ill and starving in the malarial jungles of Basilan Island, beyond help from a 5,000-member Filipino military hostage-rescue task force getting advice from 1,000 U.S. troops, AFP reported.

With the U.S. presence set to end on July 15, the couple's ordeal raises questions about the outcome of the larger U.S.-Philippines joint military effort against international terrorism.

The Kansas couple, based in the Philippines for 15 years, checked into the western island resort of Dos Palmas last year to celebrate their 18th wedding anniversary.

On May 27 the ruthless Abu Sayyaf guerrilla group, direct descendants of a slave-raiding Muslim tribe, attacked the resort and took 20 guests, including the Burnhams, and staff to their southern island stronghold.

The Abu Sayyaf, branded as a terrorist group by U.S. President George W. Bush after the September 11 attacks, then beheaded more than a dozen other captives, including U.S. tourist Guillermo Sobero.

President Gloria Arroyo agreed last November to host U.S. troops to help Bush's fight against global terrorism amid an outcry by Filipinos against kidnappings.

The arrival of U.S. special forces in Basilan in February fuelled hopes of a swift rescue for the Burnhams, as clashes became more frequent and dozens of fleeing rebels were killed or arrested.

But Arroyo kept the world's mightiest army on a tight leash, mindful of constitutional limits and local political sensibilities.

Instead of a direct combat role, she sought and got counter-terrorist training, intelligence, and help in easing the island's poverty.

Arroyo spokesman Silvestre Afable on Sunday appealed on the Burnhams' family to be more patient and assured them the military was trying its best to spring the hostages safe and alive despite "very severe climatic" conditions in Basilan.

"We are trying our best to get them out of this," he said, stressing that the military should not be embarrassed over its apparent failure to rescue the hostages despite a year-long hunt.

He new tribes mission website, which keeps a daily count of the days its missionaries have spent in captivity, acknowledges "That the best interests of U.S. and Philippine government officials are not always the best interests of Martin and Gracia." U.S. Joint Chiefs of Staff Chairman General Richard Myers visited Basilan last month and said he was satisfied with the broad progress of the anti-terror effort there. But the had no good news for the Burnham's three young children, farmed out to relatives in Wichita.