Visiting U.S. special forces troops reached the vicinity of an Abu Sayyaf stronghold in a jungle area Monday during counter-terrorism maneuvers with the Philippine military.

The four Americans were among the first of a 160-strong special forces contingent involved in a training exercise designed to wipe out the Abu Sayyaf, which has been linked to Usama bin Laden's Al Qaeda terror network believed responsible for the Sept. 11 attacks in the United States.

The American soldiers visited Maluso town on the southern island of Basilan to meet with more than 100 Philippine marines who are part of a Philippine military offensive targeting the Abu Sayyaf, which has carried out numerous kidnappings and killings in the last few years.

The U.S. soldiers are armed but can only fire in self-defense because of Philippine constitutional restrictions on the presence of foreign troops.

The Americans stayed three hours to watch a helicopter landing, eat lunch and meet with the Philippine marines. The command post was about six miles from Mount Puno Mahaji, which one Philippine marine called an Abu Sayyaf rebel "playground.''

Escorted by three Philippine marines on Monday, Americans drove two pickup trucks through coconut groves, rubber tree plantations and sparsely populated communities where rebels roamed freely before the military offensive.

Because of security concerns, the Americans were not allowed to venture out of the camp, which sits on rolling hills and is fortified by dugout bunkers. The soldiers, armed with M-4 carbines, surveyed a helicopter landing area, ate lunch and were introduced by Filipino soldiers to a 13-inch tribal machete used for combat.

"This is an outstanding jungle camp,'' U.S. Army Maj. Mark Gatto said. While he seemed relaxed, two other U.S. soldiers constantly monitored the surroundings.

The camp is also about the same distance from another area where suspected Abu Sayyaf rebels recently beheaded a Philippine military guide, underscoring risks that U.S. troops are taking as they bring the war on terrorism to the violence-prone southern Philippines.

Many left-wing groups have protested the training exercises because of possible constitutional violations and an escalation of the conflict in the impoverished southern Philippines, where other Muslim rebels are battling the government for independence.

American troops later may go to combat zones to observe Philippine troops roaming the island to search for the fewer than 100 guerrillas holding Wichita, Kan., missionaries Gracia and Martin Burnham and Filipino nurse Ediborah Yap hostage.

The small, ragtag rebel force is what's left of a violent, 2,000-strong Abu Sayyaf force that has been hammered by a nine-month military offensive involving 5,000 soldiers.

Meanwhile Monday, Philippine military officials told visiting Rep. Jim Gibbons, R-Nev., that they fear an excess of weapons from Afghanistan could end up in Abu Sayyaf possession. Officials said Gibbons told them the United States would work to prevent that.

More than 500 American troops are in the Philippines for six-month maneuvers ending in June.

Besides training, Washington also has pledged $100 million to provide weapons and equipment to help the poorly equipped Philippine military eradicate the Abu Sayyaf.

The Associated Press contributed to this report.