National intelligence director Mike McConnell said Tuesday that U.S. authorities are worried about "sleeper cells" of would-be terrorists inside the United States and are remaining vigilant against any new attacks.On the sixth anniversary of the attacks that killed nearly 3,000 people in New York, Washington and in western Pennsylvania, McConnell also said plots against the United States have been thwarted. But he said there can make no safety guarantees.
"We're safer but we're not safe," he said in an interview on ABC's Good Morning America.
McConnell said that Osama bin Laden's al-Qaeda terrorist network "intends to have an operation in the United States that will result in mass casualties."
Read More
