WASHINGTON (AP) — The failed Times Square bombing exposed the unsolved threat hidden among the massive flow of Americans going abroad: Homegrown jihadists who travel undetected to terrorist havens, link up with insurgents and carry back plots aimed at the homeland.

As the U.S. and other countries put more pressure on militants overseas, terror groups are now more actively wooing Americans, who don't face as much scrutiny when they travel, U.S. authorities say.

"I think there is a calculated decision being made by some in the al-Qaida leadership to look for people who might have more access" to the U.S., said Air Force Gen. Gene Renuart, former head of U.S. Northern Command, in an interview with The Associated Press.

"Al-Qaida is having difficulty growing jihadists in some of the areas where they have safe haven because of the pressure that has been put on them, so they seem to be looking for people who have no previous connections and trying to radicalize them," said Renuart, who retired this week after 39 years of military service.

The Times Square case is reinforcing concerns in Congress about gaps in the government's patchwork system to find and track homegrown militants on the move. These citizens, who quietly take on jihadi beliefs but have no apparent terrorist background or ties, set off no alarms as they cross in and out of the U.S.

"It goes right to the heart of the challenges we face," FBI spokesman Paul Bresson acknowledged. "But I can tell you we have dedicated people working tirelessly and around the clock using all available lawful tools and methods to identify and disrupt potential plots."

Every year hundreds of thousands of U.S. citizens go back and forth to countries known to house terror groups and training camps, such as Pakistan, Somalia and Yemen.

The U.S. system for finding and tracking homegrown terrorists among them depends largely on constantly updated travel records, screening by sharp-eyed border and law enforcement officials, and some intelligence-sharing with foreign governments.

U.S. Customs and Border Protection keeps records on people who travel in and out of the U.S. Officers can pull up information to see who a known suspect was traveling with on a certain date.

But unlike the recently upgraded air security system, which is aimed at terrorists flying on U.S.-bound airlines, the ability to find and track the movements of homegrown jihadis is sharply limited by the sheer volume of travelers and the rights of Americans to travel freely.

In the Times Square case and in a spate of homegrown terrorist plots over the past year, the suspects were not known to be extremists when they went abroad, and their names were not on U.S. watch lists.

Times Square bombing suspect Faisal Shahzad, a Pakistan-born U.S. citizen, had traveled to Pakistan last year and returned to America in February. But officials say there was no information available that would have led authorities to suspect he was involved in terrorist activity.

New York subway bomb plotter Najibullah Zazi was also able to travel to Pakistan under the radar because he too was living in the U.S. legally and had no record of terror connections. The Afghan-American al-Qaida recruit from a Denver suburb pleaded guilty in February for leading a plot to bomb the New York subway system.

Others who have gone abroad to link up with terrorist networks include Long Island native Bryant Neal Vinas, who pleaded guilty to terrorism charges in January. Five Washington area men now on trial in Pakistan for planning terrorist attacks also are accused of such activities.

A former U.S. intelligence official said the CIA does not monitor Pakistani-Americans overseas unless the FBI has specific information linking them to terrorism. The CIA works with Pakistan's intelligence service, the ISI, in those situations, said the former official, who spoke on the condition of anonymity in order to discuss the sensitive matter.

Pakistan shares information with U.S. officials in scrutinizing American travelers but its oversight is also limited. Pakistani officials check visas and travel documents of all Americans arriving at the country's airports, said a senior Pakistani federal overseeing terrorism and immigration.

Pakistani officials also scan a database to check whether the arriving passengers are involved in any "unwanted" activity, said the official, who spoke on condition of anonymity because he was not authorized to speak to the media.

But another top Pakistani official conceded there was room for improvement. "There is a need to keep better track of people," said Tariq Pervez, head of Pakistan's National Counterterrorism Authority. "There needs to be coordinated action in the host countries and the countries of origin of terrorists."

Concerned about the continuing ability of homegrown militants to go abroad and return to carry out plots, lawmakers last week called on U.S. authorities to do a better job tracking and analyzing the travel of Americans to terror havens.

Rep. Adam Smith, D-Wash., and a member of the House intelligence committee, said he believes it is appropriate, in light of recent events, to take a close look at people who travel to countries known to have terrorist havens. The key, he said, is to identify people who have connections to al-Qaida or to terror groups that are training recruits to threaten the U.S.

The vast numbers are a stiff challenge. For example, in 2009, 172,000 passengers traveled back and forth between the U.S. and Pakistan, according to U.S. government data.

Any effort to expand monitoring of American travelers also raises privacy concerns and logistical challenges, particularly the prospect that travel patterns might be cross-checked against credit card purchases, phone calls or other personal data.

"I think there's good reason, not only from the privacy and civil liberties perspective but also in terms of effectiveness, to look closely at these proposals to expand tracking of the travelers," said Marc Rotenberg, executive director of the Electronic Privacy Information Center. "It is not clear at this point that enhanced tracking promotes greater security."

In the short term, officials said, the U.S. must get better at culling the endless intelligence on potential threats that pours in every day.

Paul McHale, the Pentagon's former assistant secretary for homeland defense, said the U.S. needs to be able to assimilate large amounts of data far more quickly, through the use of more sophisticated computer programs.

"The challenge is identifying threat patterns within that data in a way that is sufficiently timely to prevent an attack," said McHale, now a member of McKenna Long & Aldridge law firm in Washington.


Associated Press writers Eileen Sullivan and Adam Goldman in Washington and Kathy Gannon and Zarar Khan in Islamabad contributed to this report.