A military unit has expanded its role in supporting the hunt for terrorists trying to slip across the Mexican and Canadian borders.

BY JOSEPH L. GALLOWAY

EL PASO, Texas - There's a growing sense of urgency among those who police America's long, porous borders that tighter control is needed to prevent terrorists from slipping into the flood of illegal immigrants entering the United States.

The Sept. 11 commission found that the nation's borders are largely unprotected and recommended that border security become an integral part of national security policy. Now that airline security has been improved, terror suspects increasingly are being detected trying to enter the country on ships or overland.

A military unit called Joint Task Force-6 is greatly expanding its role in supporting the hunt for terrorists trying to slip across the Mexican and Canadian borders.

CONTROL CENTER

A modern control center at its headquarters at Fort Bliss in El Paso, which starts operations next month, will gather feeds from U.S. intelligence agencies. And the commander of JTF-6 gets military Reserve units from all over the country to volunteer for missions along the southern border. He tells them there's no better place in America to get the kind of training that will prepare a unit for deployment to Afghanistan or Iraq.

Units come here for two weeks at a time, in lieu of ordinary summer training back home. This month, Army Reserve engineers from New York were out in the 115-degree heat building roads on the border at Nogales, Ariz. Marine Reservists flying Super Cobra helicopter gunships were helping the Border Patrol by scouring the border at night.

Since the 2001 terrorist attacks, the government has directed more resources at tightening border security. Still, the commander of JTF-6, Brig. Gen. John ''Jay'' Yingling, said his nightmare is that al Qaeda terrorists will slip in with illegal immigrants and attack the United States again.

Authorities see Latin America as a potential recruiting ground for terrorist groups because it has weak governments and police, drug smuggling conduits for moving people and goods and its own lax border controls.

Some recent developments have heightened concerns:

• Authorities in Tegucigalpa, Honduras, have received information suggesting that a group linked to al Qaeda has been planning attacks on the British, Spanish and American embassies. Security was increased around the embassies on Friday.

• Other police reports suggest at least one Saudi-born member of al Qaeda, Adnan el Shukrijumah, may have been in Tegucigalpa in July, having crossed the border illegally from Nicaragua after a stay in Panama.

INTERAGENCY CONCERN

Yingling and his bosses at the U.S. Northern Command in Colorado hope to see Joint Task Force-6 become an interagency operation that will get all law enforcement and intelligence agencies on the same sheet of music.

Yingling has built a modern state-of-the-art control center at JTF-6 headquarters at Fort Bliss to coordinate and sharpen the impact of law enforcement.

''There is too much stove-piping of information and intelligence,'' Yingling said. ``The events of 9/11 are a striking catalyst for change. We need to bring it all together -- human intelligence, signal intelligence, radar, all of it -- to be more effective, more pro-active.''

Last year, the U.S. Border Patrol apprehended more than 900,000 illegal immigrants who were trying to get across the border. Some agencies estimate that for every one apprehended, four others make it across and disappear.

What JTF-6 watches most closely are ''special interest aliens'' -- those whose native countries are of high interest in the global war on terrorism. The Border Patrol detained 303 such people crossing the border from Canada last year and 262 crossing from Mexico.

MORE MANPOWER

Carl L. McClafferty, the deputy chief of the Tucson Sector of the Border Patrol, said his agency has increased manpower in the stations along the Arizona border, doubling and even tripling the number of agents.

After heightened security made smuggling difficult in the high-traffic areas of San Diego and El Paso, smugglers rerouted the flow of aliens and drugs toward Arizona. The Border Patrol then built 14-foot-tall steel fences and installed 60-foot-tall towers equipped with detection equipment for several miles through each of the major crossing points in Arizona.