Attorney General Eric Holder has an urgent message for Americans: While he is confident that the United States will continue to thwart attacks, "the terrorists only have to be successful once."
And while it is not certain we will be hit, the American people, he told ABC News, "have to be prepared for potentially bad news."
"What I am trying to do in this interview is to make people aware of the fact that the threat is real, the threat is different, the threat is constant," he said.
In a rare and wide-ranging interview, the attorney general disclosed chilling, new details about the evolving threat of homegrown terror, and touched on topics ranging from Wikileaks to the prisoners at Guantanamo Bay.
What was uppermost on his mind, however, is the alarming rise in the number of Americans who are more than willing to attack and kill their fellow citizens.
"It is one of the things that keeps me up at night," Holder said. "You didn't worry about this even two years ago -- about individuals, about Americans, to the extent that we now do. And -- that is of -- of great concern."
"The threat has changed from simply worrying about foreigners coming here, to worrying about people in the United States, American citizens -- raised here, born here, and who for whatever reason, have decided that they are going to become radicalized and take up arms against the nation in which they were born," he said.
In the last 24 months, Holder said, 126 people have been indicted on terrorist-related charges, Fifty of those people are American citizens.
"I think that what is most alarming to me is the totality of what we see, the attorney general said. "Whether it is an attempt to bomb the New York City subway system, an attempt to bring down an airplane over Detroit, an attempt to set off a bomb in Times Square ... I think that gives us a sense of the breadth of the challenges that we face, and the kinds of things that our enemy is trying to do."
Holder says many of these converts to al Qaeda have something in common: a link to radical cleric Anwar Al Awlaki, an American citizen himself.
Authorities suspect Awlaki helped mastermind last year's Christmas Day underwear bombing plot in Detroit, and a recent scheme to blow up cargo planes travelling from Yemen to Europe and the United States.
"He's an extremely dangerous man. He has shown a desire to harm the United States, a desire to strike the homeland of the United States," Holder said. "He is a person who -- as an American citizen -- is familiar with this country and he brings a dimension, because of that American familiarity, that others do not."
Holder said that as a threat to the United States, Awlaki ranks right up there with Osama bin Laden.
"He would be on the same list with bin Laden," the attorney general said. "He's up there. I don't know whether he's one, two, three, four -- I don't know. But he's certainly on the list of the people who worry me the most."
When asked whether the United states has a preference between killing or capturing and prosecuting Awlaki, Holder replied: "Well, we certainly want to neutralize him. And we will do whatever we can in order to do that."
Awlaki is believed to be in Yemen, but thanks to the Internet, his reach is global, and his influence dangerous.