In prepared text seen in advance by the New York Times, John Scott Redd, a retired vice admiral who heads the National Counterterrorism Center was to tell the Senate Homeland Security and Governmental Affairs Committee the battle hadn't been won at home or abroad.
"We are safer than we were on Sept. 11, 2001," the text says. "But we are not safe. Nor are we likely to be for a generation or more."
Robert Mueller, the director of the FBI, also issued a cautionary note about the threat of domestic terrorists in his prepared text.
"Although we assess that the level and intensity of extremism inside the United States does not equal that in the United Kingdom or elsewhere in Europe, we are well aware that we have extremists in the United States who wish to do us harm," Mueller's script said.
Swim Week Miami Beach 2014 [PHOTOS]