The warning last month from Rep. Peter King, the chairman of the House Committee on Homeland Security, was blunt: An investigation by his staff had determined that "hundreds" of people he described as "Iranian and Hezbollah terrorists" were in the United States.
But interviews with U.S. intelligence and law enforcement officials, as well as private experts, about the Iranian-sponsored group paint a more nuanced picture. There is a threat, though whether it is imminent or extensive is far from clear, they say.
An alarming part of the officials' assessments focuses on the apparent surveillance missions that Iranian diplomats and possible Hezbollah operatives have been seen conducting at sensitive targets such as New York subways and bridges, and at nuclear power plants and tunnels elsewhere in the United States in the past 10 years.
At the same time, U.S. officials caution that Hezbollah, a Shiite militia based in Lebanon, has largely avoided attacking U.S. targets since it carried out mass-casualty bombings in the 1980s against the U.S. Embassy and Marine barracks in Beirut. One reason may be that it does not want to endanger its lucrative North American fund-raising operations.
The renewed focus on Hezbollah — which U.S. counter-terrorism officials regard as the most potent and disciplined of Islamic militant groups, even more so than al-Qaida — comes amid a growing confrontation over Iran's nuclear program.
An Israeli or U.S. strike on Iran's nuclear sites could prompt Hezbollah to change strategy, moving from surveillance and fund-raising in North America to launching retaliatory attacks on either country, several U.S. officials said. They spoke on condition of anonymity to discuss security matters.
BROADER RISKS DOWNPLAYED
Israel's leaders, while acknowledging the likelihood of retaliation by Iran or its agents, have sometimes downplayed the risk of a broader conflict.
Iranian-inspired surveillance missions in the United States have been scattered over a period of years. But, when combined with a handful of recent attacks or plots around the world, they have contributed to an assessment within the U.S. government that considerable violence directed against U.S. targets — at overseas installations or businesses, or at American soil — could follow any strike on Iran's nuclear program.
U.S. intelligence and law enforcement officials, along with private experts, say there is little doubt Hezbollah has an extensive network of supporters, fund-raisers and potential operatives in the United States.
A law enforcement official said that the New York Police Department, whose monitoring of Muslim communities has prompted political controversy, believes that between 200 and 300 Hezbollah sympathizers live in New York City. Between 10 and 20 of those are relatives of Hezbollah leaders or fighters who were killed in action, said the official.
The NYPD's knowledge of Hezbollah's infrastructure is sufficiently detailed that it has identified three Lebanese towns — Bint Jbeil, Yanoun and Yatar — to which suspected sympathizers of the group have ties. At least a handful of people in New York connected with Hezbollah have also undergone military training in Lebanon, the official said.
A preliminary report issued by investigators for King, a New York Republican, said that pinpointing the number of Hezbollah operatives inside the United States was difficult because of the group's operational security. The committee report nonetheless cited the estimates of "some officials" that the group "likely" has "several thousand sympathetic donors" in the United States as well as "hundreds" of operatives.
But other officials familiar with up-to-date U.S. intelligence on Hezbollah said there was a big difference between a Hezbollah "supporter" and someone who would be willing to engage in violent activity. The officials said such distinctions have been blurred in public discussions about the domestic threat the group allegedly poses.
Over the years, U.S. federal authorities have brought numerous criminal cases against alleged Hezbollah operatives, most of them related to fund-raising or other support activity rather than plotting against U.S. targets.
The access to potential funding sources is one reason why Hezbollah has avoided targeting the United States or its interests, said Evan Kohlmann, an investigator who monitors militant websites for the government and private businesses.
"For the last 15 years, Hezbollah has regarded North America as a piggy bank," Kohlmann said.
Reliable figures for Hezbollah's fund-raising, which is done covertly, are not available.
Because the United States is such a critical source for funds and equipment such as night-vision devices that might be useful to its paramilitary operations, Kohlmann said, Hezbollah might be reluctant to embark on attacks inside the United States — even if prodded to do so by patrons in Iran. Attacks against U.S. targets overseas might be more likely, he said.
Kohlmann said that Hezbollah regards the United States as such an important supply point that the group supposedly has planted its own "procurement manager" somewhere in North America.
One factor heightening U.S. officials' concern about Hezbollah-related attacks is the accumulation of accounts of alleged attempts by Iranian operatives to "case" potential U.S. targets.
According to a New York law enforcement source, there have been several notable incidents of this nature involving individuals who turned out to be accredited to Iran's U.N. mission.
In a 2003 incident, New York police patrolmen observed a group of men videotaping the tracks out of the front window of a subway train traveling between Queens and Manhattan at 2 a.m. The Iranians were arrested, but later released after they produced diplomatic credentials. The law enforcement source said they were asked to leave the country.
In a 2006 incident, the captain of a sightseeing boat became suspicious after a group of Iranians taking his cruise along the East River broke into two smaller groups and started snapping pictures of the undersides of the Brooklyn and Manhattan bridges. The six men all turned out to be covered by diplomatic immunity, the law enforcement source said.
In September 2008, three more Iranians with diplomatic status were observed taking pictures of rail tracks going into Grand Central Station that are not routinely accessible to members of the public.
And in a 2010 incident, security personnel at a heliport near Wall Street observed a group of men who claimed to be affiliated with an Iranian broadcasting network taking pictures of the framework supporting the heliport deck which was cantilevered over the river.
A federal official said that similar surveillance incidents had been reported in other cities such as Los Angeles and Las Vegas. Targets under observation included nuclear power plants, tunnels and casinos.
Some of the officials said that anxieties about possible Hezbollah- or Iranian-related attacks were increased in the wake of an alleged plot by Iranian agents to kill the Saudi ambassador in Washington and other alleged Iranian plots uncovered recently in Thailand, India, Azerbaijan and Georgia.
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