Washington: A decade after the 9/11 attacks, America faces less risk from a repeat massive terror strike than from a smaller, less deadly hit which could prove harder to detect, the country`s domestic security chief said on Wednesday.
"What we see instead are smaller plots involving fewer people so they are much more difficult to intercept," US Homeland Security Secretary Janet Napolitano said at an event held at the US Chamber of Commerce.
"We have a layered system of security that gives us multiple ways in which to interrupt that large complicated plot," Napolitano said.
"But we are also seeing the rise of the activity by individuals who are actually in the country and they are acting by themselves," she said.
"That kind of attack is the most difficult to prevent because there is nothing to intercept," Napolitano said.
She made her remarks at the forum held less than a month before the anniversary of the 2001 al Qaeda assault on the Pentagon and Manhattan`s World Trade Centre complex.
Napolitano said overall US domestic security is greater than it was before September 11, 2001, when the nation suffered the deadliest attack ever on the United States.
"There is no question that our country is stronger and more secure against those kind of attacks than a decade ago," Napolitano said. "We have made progress on every front."
Her comments echoed remarks one day earlier by US President Barack Obama, who said he worried about a possible terror strike on US soil by a solitary extremist.
"The most likely scenario that we have to guard against right now ends up being more of a lone wolf operation than a large, well coordinated terrorist attack," he told CNN television during a campaign-style swing through the US heartland state of Iowa.
"When you`ve got one person who is deranged or driven by a hateful ideology they can do a lot of damage and it`s a lot harder to trace those lone wolf operators," Obama said on Tuesday.
He said US officials were "constantly monitoring potential risks" but said a punishing US campaign had left al Qaeda "a much weaker organisation with much less capability than they had just two or three years ago”.