By Simon Ingram In Isabela, southern Philippines

The narrow streets of Isabela city, on the southern Philippines island of Basilan, do not often reverberate to the rhythm of fiesta drums.

Last week was the first time in years that the provincial capital staged large-scale public festivities, defying security fears linked to long decades of violence between government forces and the various rebel groups that operate on the island.

The US troops could stay longer than planned

The US forces on Basilan have brought local people an added sense of security and are also helping improve the area.

But there are also suspicions that the US hopes to establish a permanent military base in the region.

Military bulldozers, excavators and other heavy equipment arrived recently to work on improving the roads and other infrastructure in this, one of the Philippines' most impoverished regions.

Work on upgrading some 60 kilometres of Basilan's roads has already begun. Repairs to bridges and piers on the island's shoreline will follow, along with the digging of new deep water wells.

While the Pentagon's PR machine stresses the long-term benefits of all this work to civilians, Major Tony Ference of the US Marines says the immediate objectives are to help eradicate the rebels of the Abu Sayyaf, which the US links with the al-Qaeda network.

Local uncertainty

The Abu Sayyaf says it is fighting for a Muslim homeland. But its main activity has been kidnap for ransom. It has been holding hostage a US missionary couple, Martin and Gracia Burnham, for nearly a year.

Of course the long-term aim is to establish a listening post in Mindanao

Marites Vitug, writer

Media and public alarm over the Abu Sayyaf and other radical Islamic groups reached fresh heights following several recent - and still unexplained - bomb attacks in the main southern island of Mindanao that killed 15 people.

The majority Christian community is grateful for US help in crushing the Abu Sayyaf.

But Father Angel Calvo, an activist working to build inter-communal understanding in the southern Philippines, says many Muslims - even those who abhor the Abu Sayyaf - see the deployment of hundreds of foreign troops as somehow directed at them.

"I understand how the people welcome the presence of the American soldiers at this moment," he says. "But we also have to say that it has been the point of increasing the gap, the division between the two communities, the Muslim and the Christian community."

Wider motive?

With joint field exercises involving Philippine and American troops now well under way, there is talk of extending them beyond their scheduled six-month term. The lack of visible progress in eradicating the Abu Sayyaf and freeing their two US hostages is one explanation.

But the Pentagon's broader strategy here may be another.

"Of course the long-term aim is to establish a listening post in Mindanao whereby they can watch the terror network in South East Asia, like Malaysia and Indonesia," says Marites Vitug, a writer with extensive knowledge of the Mindanao region.

"Because after all, the US doesn't have any mutual defence treaty agreements with these two countries. We're the only ones they have such an agreement with - they can fly in and out, they can refuel here, they can stay, but not permanently.

Back at the fast-expanding US army encampment in Basilan, the sight of builders hard at work on a new headquarters is enough to reinforce such suspicions, especially among those Filipinos who criticised these joint exercises from the start.

The Americans came here saying Basilan was a new but localised front in the war on terrorism. It could end by providing Washington with the means to strike at what it perceives as a much broader threat to US interests.