Homeland Security chief Michael Chertoff warned Thursday that the radical Islamic group Hezbollah "makes Al Qaeda look like a minor league team," and poses the greatest threat to national security.
"Someone described Hezbollah like the A-team of terrorists in terms of capabilities, in terms of range of weapons they have, in terms of internal discipline," Chertoff told FOX News. "To be honest, they make Al Qaeda look like a minor league team.
"They have been more disciplined, and they've been in some senses more restrained in the kinds of attacks they carry out ... in recent years, but that's not something we can take for granted," he warned.
Chertoff, speaking before the opening of a two-day terrorism forum in Jerusalem, also warned of the threat of a terrorist smuggling a bomb aboard a passenger airplane.
"I don't think we're really worried about hijacking because we've put a lot of measures in place like a locked cockpit door, flight deck officers who have weapons and the air marshals," Chertoff told FOX News. "So the next threat becomes the bomb. Something that either a person takes on board themselves or smuggles into the cargo."
"One way we've addressed smuggling a bomb is by reducing the size of liquids you can bring on board," Chertoff said. "That was a direct result of learning terrorists had developed a way to disguise liquid explosives.
"The second thing we're in the process of doing is intensifying the degree of screening we use for baggage that goes into the cargo. Whether it comes from the passenger or is shipped from company. All of this is raising the level of defense," he said.
Hezbollah, which represents most of the Shia in Lebanon and whose related factions hold a combined 37 seats in parliament -- more than a quarter of the legislative body -- is openly dedicated to the destruction of Israel.
In a 2000 interview with the Washington Post, Hezbollah leader Hassan Nasrallah said, "I am against any reconciliation with Israel. I do not even recognize the presence of a state that is called 'Israel.'"
Military analysts estimate Hezbollah's armed strength to be about 1,000 full-time highly trained members, with as many as 10,000 volunteers who openly patrol the streets of Beirut and other Lebanese towns.
The group's primary weapons are believed to consist of an arsenal of Russian- and home-made rockets, as well as arms supplied through Iran, the group's political and spiritual ally.
In addition to Chertoff, the two-day security forum, hosted by Israeli Minister of Internal Security Avraham Dichter, includes representatives of Canada, Germany, France, Spain, Poland, Italy, the United Kingdon and the Palestinian Authority.
Part of the agenda will cover the psychology of bombers and a demonstration by Israeli security experts of how to foil an airplane hijacking.
FOX News' Reena Ninan contributed to this report.