Updated

In a major expansion of American military involvement in the Philippines, hundreds of U.S. special operations troops will soon take front line combat roles against Abu Sayyaf rebels, officials say.

Unlike previous arrangements in which U.S. troops played advisory roles out of the line of fire, the American and Philippine governments agreed to place U.S. troops alongside Philippine soldiers in direct combat, defense officials said Thursday. They spoke on condition of anonymity.

White House spokesman Ari Fleischer, while declining to discuss details of the military operation, said it was "another example of where the world stands united" in the battle against terrorism.

He called the Abu Sayyaf group "a deadly organization" that could not be allowed to have their way. Fleischer briefed reporters in Crawford, Texas, near the president's ranch.

The joint offensive is expected to start in March, with the exact date to be determined by the Manila government.

Several terrorist groups, some with suspected links to Al Qaeda such as the Islamic extremist network Jemaah Islamiyah, operate in the Philippines and there have been a series of deadly bombings, kidnappings and other attacks against both government and civilian targets. An Oct. 2 incident blamed on Abu Sayyaf killed three people, including a U.S. Green Beret in Zamboanga.

Pentagon officials say investigations following some of those attacks have turned up information indicating the link between the Abu Sayyaf and the Jemaah Islamiyah of Indonesia may be stronger than earlier believed.

About 350 U.S. special operations forces, mostly Army Green Berets, will be involved in the offensive in the Sulu Archipelago, with much of the effort focused on the island of Jolo, the officials said. They will be supported by about 400 more U.S. troops based to the north in the port city of Zamboanga.

In addition to the U.S. special operations forces and the support personnel, a team of about 1,000 Marines aboard Navy ships off the coast of the Sulu Archipelago will be available to respond on short notice with air power, logistics help and medical aid, the U.S. officials said.

The Marines are part of the Okinawa-based 31st Marine Expeditionary Unit, and their lead ship is the USS Essex, based at Sasebo, Japan.

It was not immediately clear how many Philippine forces would be involved in the offensive.

In Manila, however, a Philippine official denied such an agreement had been reached and said allowing U.S. troops to engage in combat could be illegal.

"I am categorically saying that anything that they say that contradicts the constitution and the laws will not materialize," Defense Secretary Angelo Reyes said Friday. He dismissed the statements by the unidentified U.S. officials as leaks.

Reyes said he planned to fly to Washington on Sunday for talks with Defense Secretary Donald Rumsfeld on "defense and security-related issues of mutual interest." He said the trip had been scheduled before the controversy over U.S. involvement in combat.

U.S. officials have said in recent days that they have new information showing a stronger link than previously believed between the Philippine rebels and other international terrorist groups.

The government of Philippine President Gloria Macapagal Arroyo said Monday that she had approved joint training with U.S. forces on Jolo, where some Abu Sayyaf rebels fled after the previous U.S.-Filippino effort last year to root them out of Basilan island, to the north of Jolo.

U.S. officials said the March offensive would go well beyond training to include direct combat roles for U.S. forces.

The purpose, one official said, is to "disrupt and defeat the Abu Sayyaf group." He said the effort had no time limit and would continue as long as both governments agreed it was needed.

There are believed to be several hundred Abu Sayyaf rebels in the Philippines. Early this month the Philippine military announced it had greatly underestimated the number of Abu Sayyaf and warned it would take a long time to wipe them out.

A Department of National Defense report submitted to the Philippine Congress late last year placed their strength at 250, down from 800 in 2001. But Chief of Staff Gen. Dionisio Santiago acknowledged Feb. 5 that a recheck of military documents and figures showed a number closer to 500 — most on the impoverished island of Jolo.