By Matt Frei BBC Asia Correspondent

There is much speculation about where the US-led war against terror is going next - but in a quiet way, the war has already been extended.

More than 600 US soldiers are on the ground on the southern Philippine island of Basilan.

They are there ostensibly to help the Philippine army in its hunt for Muslim rebels - members of the Abu Sayaf group - who are said to have links with al-Qaeda.

US troops hope to win the support of the local people

Basilan Island looks very alluring. The turquoise waters of Suli Sea, the bright blue sky, the fishing boats on the horizon, the palm trees on the shore, the houses on stilts.

But it is one of the poorest and most lawless corners of Asia. The place is notorious for kidnapping and we were even advised by the authorities not to come here.

It is the latest and the most far-flung front line in America's war against global terrorism. Operation Enduring Freedom - part two.

American Chinook helicopters landing in the dense jungle of South East Asia are disgorging hundreds of heavily armed special forces.

Camp atmostphere

This could not be more different to the war on terrorism as we have known it so far in Afghanistan. At one military camp, Campo Uno, we are right in the middle of the Filippino jungle surrounded by palm trees.

We're fighting for the sympathy and support of the villages here

Lieutenant Colonel Daniel Lucero

It is incredibly hot and humid, and to be honest, the atmosphere in this camp is rather relaxed, almost a sort of village atmosphere.

You have got US special forces having a coke and some orangeade sitting in one area and Filipino soldiers on the other side of the camp being trained.

In the hills close to the camp there is a dense jungle where you really cannot see further than 20 or 30 yards. That is where the Abu Sayyaf are thought to be hiding and the task here is to find these people and root them out.

Abu Sayyaf means "bearers of the sword". There are only about 100 alleged members of the group and 8,000 Filippino soldiers chasing them, so far unsuccessfully. The Americans are here to help them defeat this elusive enemy.

"They're very difficult to track, they're very difficult to find," says Major John Deitrich. "We have a very good armed forces here that we're working with in the Filipino armed forces.

"It's a very capable force, it's just that working in the jungles and trying to get them away from their popular support base is the real difficulty in dealing with this group.

"This is a very thick, very vegetated, very rough and steep terrain."

Rebels' appeal

On this predominantly Muslim island the Americans are just as alien as the Christian Filipino soldiers who have been fighting the local insurgents for decades.

The US is in the region to train the Filipino soldiers

Lieutenant Colonel Daniel Lucero is in charge of the army battalion and knows just how difficult it is to win this war.

"We're fighting for the sympathy and support of the villages here and we have to gain their sympathy because they give refuge and shelter to these Abu Sayyaf members," he says.

"The Abu Sayyaf is offering a new kind of governance to the Islamic system, and I think they have gained some ground on convincing some of the villagers that their kind of government is much better than our democratic system."

We were taken to a local jail to see some of the Abu Sayyaf suspects languishing behind bars. Most of them are no older than teenagers and they all deny being terrorists.

It is hard to imagine how these boys can have links to Osama Bin Laden or al-Qaeda but it is also easy to imagine how they can be persuaded to join in extremist groups in a backwater that offers them no future.

"I have no proof that they are really linked to al-Qaeda," says Kandu Marit, a former rebel turned city councillor.

"As far as Basilan is concerned the solution only is gun and bullet which I do not believe that our problem can be resolved by... because we have been in this problem for 30 years already.

"So we have to work out the solution to the problem without bullet and gun."

American choppers plough the skies above Basilan by night and by day. A year ago this island was as obscure as the Abu Sayyaf. Now American soldiers are on the ground in the jungle risking their lives.

It is another indication of how 11 September has changed the world.