Hundreds of US troops have been working in the southern Philippines since 2002. Their role is to help train local soldiers in the battle against insurgents, and their presence divides local opinion. The BBC's Vaudine England reports from Manila.
Philippine troops have been battling insurgents for decades
It is one of the most ignored, but perhaps one of the most successful, fronts in the Bush administration's so-called War on Terror.
As part of the Joint Special Operations Task Force,
US troops train their Philippine counterparts in counter-terrorism and provide financial and logistical support.
Their presence coincides with a stepped-up US aid budget enabling better roads, schools, clinics, ports and more.
Officially the US troops are not involved in any combat operations. In US embassy words, the programme combines the "iron fist and hand of friendship".
Yet there are many conspiracy theories about what the troops are doing - ranging from eavesdropping on Indonesia to buying the way back into a permanent military presence in the Philippines, which the US lost in 1991.
Tom Green of Pacific Strategies and Assessments, a Manila-based security company, argues that both of these theories are nonsense.
"The US is seeing a regional terror threat and sees the south [of the Philippines] as a potential free haven and incubation area for more radical elements," said Mr Green, a former US military officer.
"The US role is training and assistance, as part of a long term effort to develop local capabilities."
US-Philippine military co-operation sparks occasional protests
He says the US is taking a low profile because this approach is more sustainable.
"If you've got a constructive presence in a village, you've hopefully got a medium to long term contribution to employment, to health, to education," he said.
"And, more tactically, with a constructive relationship with the villagers, they start talking to you."
There is some support among Filipinos, but concerns persist - both about sovereignty and about what the US presence might be doing to already delicate relationships in the south.
Independence groups from the Muslim minority Moro people were fighting the Manila government three decades before the War on Terror was declared.
Peace talks are now in progress between the Moro Islamic Liberation Front (MILF) and the Manila government.
But the Abu Sayyaf group, long seen within Asia as a gang of kidnappers and smugglers, continues to pose a threat to law and order.
In the 1990s, Philippine military intelligence officers told me that hundreds of Indonesian militants were training with their Muslim brothers in the south.
Members of the Indonesia-based Jemaah Islamiah (JI) militant group have sought refuge and practised bomb-making in the Philippines.
Earlier this month the Philippine authorities announced the arrest of three suspected militants plotting to bomb foreign embassies in the capital. The Rajah Solaiman Movement, a home-grown militant group, has also been linked to Abu Sayyaf and JI.
'Second coming' of US
Sometimes opposition to the US troops is expressed as an ideological aversion to any foreign presence in the Philippines - which was once an American colony.
Julkifli Wadi, a professor at the Islamic Studies Institute of the University of the Philippines, argues that "neo-colonialism" is an inadequate word to explain the US role in his country.
Instead, he says, the south is suffering from "multiple colonialisms" with the War on Terror amounting to the "second coming" of the US.
"On the one hand, the Philippines government is able to make her presence felt on the radar screen of US foreign policy and therefore receive hefty financial assistance, making it appear that there is indeed a threat," he said.
On the other hand, he believes that the US is "using the Philippines as a cover for its wider engagement in the region".
To other analysts, the labelling of undesirables as Abu Sayyaf or other terrorists is imprecise and perhaps disingenuous.
"Our feeling is that Abu Sayyaf is decimated," said Amina Rasul, director of the Philippine Council for Islam and Democracy think-tank.
"The other group they're trying to hunt is Jemaah Islamiah, but already last year they were only talking about two possible leaders" hiding in the area.
"Is this something that requires the combined forces of the Philippine and US militaries? I'm not so sure," said Ms Rasul.
She notes that, in Indonesia and elsewhere in the region, successful counter-terrorism has been led by local police, not foreign soldiers.
"The more we look at the situation in the south, the more many of us realise they should be strengthening the capacity of local police agencies.
"First, they are local, they know local intelligence, they are plugged into local networks. Any act they do against terrorists will never be seen as a move of the non-Muslim majority against a Muslim community," said Ms Rasul.
Measuring the size of the threat against the size of the US presence is difficult - official numbers are not made public.
Mars Buan, a senior analyst with the Pacific Strategies and Assessments, estimates Abu Sayyaf had about 200 fully armed members at the end of 2007, down from about 400 in 2005-06.
US forces amount to about 500 troops on rotation, in addition to visiting "advisers" and other personnel for "training surges".
Many of these are on civil-military operations, but the bulk of the US contingent is believed to be made up of special forces.
The apparent success of foreign troops in building infrastructure in the troubled region highlights, above all, a failure of local governance.
If Philippine government bodies could manage their resources to shelter and assist their own people, maybe all those special forces could go home.