A US Capitol police officer guards the West steps of the US Capitol building, May 26, 2006. US intelligence and law enforcement authorities are discovering new home-grown cells of Islamist radicals in the United States that draw inspiration and moral support from al Qaeda, officials said on Tuesday. [Reuters]

US intelligence and law enforcement authorities are discovering new home-grown cells of Islamist radicals in the United States that draw inspiration and moral support from al Qaeda, officials said on Tuesday.

Like local terrorism cells that have recently come to light in Canada and Europe, officials said the groups are comprised of disaffected young men in their teens and 20s who rely on the Internet to try to organize and plan potential attacks on the US homeland.

Concern about attacks inside the United States gathered pace after the arrest earlier this month in Canada of 17 men -- all Canadian citizens or residents -- accused of planning al Qaeda-inspired attacks across densely populated southern Ontario.

Scott Redd, director of the National Counterterrorism Center, said in a written statement to the Senate that the emergence of home-grown terrorist groups is posing "real challenges" for US authorities despite law enforcement successes at disrupting potential attacks.

"We are grappling with a whole new set of questions: what forces give rise to this violent ideology in immigrant communities that may appear otherwise to be quite well assimilated? ... What signs should we be looking for to try to draw early warning of potential problems?" the statement said.

In later oral testimony, Redd said home-grown cells were a new domestic phenomenon for which the FBI and law enforcement agencies had no "baseline" for measuring the scale of the problem.

Redd declined to discuss details with senators in public but cited recent arrests of terrorism suspects in California and Georgia.

"That's three in a little over a year, and there are obviously other investigations ongoing," Redd told the committee.

US Sen. Joseph Biden of Delaware, the panel's ranking Democrat, said the emergence of home-grown US terror cells is widely recognized within the intelligence community.

"Everyone I've spoken to in the intelligence community says there are more cells now in the United States, there's more activity in the United States," Biden said.

Intelligence officials have long warned the international battle against al Qaeda had encouraged Islamist militants to operate in small groups like the cell that carried out bombings in London in 2005.

The Bush administration has also pointed to the flexibility of al Qaeda operatives as justification for President George W. Bush's domestic spying program, which has caused an outcry by allowing the National Security Agency to eavesdrop on US citizens without a warrant while in pursuit of militants.

Biden noted that word of new cells inside the United States comes at a time when the Bush administration has proposed 40 percent cutback in counterterrorism funding for New York and Washington -- the two cities hit in the September 11 attacks.

He also blasted the administration for not meeting security funding recommendations by the September 11 commission.

"We're spending $740 million for the whole shooting match and the recommendation is $44 billion over five years," the Delaware senator said.

"I find it absolutely on the verge of criminal."