Clapper also told the House Intelligence Committee during a hearing on worldwide threats that another top priority for U.S. intelligence is preventing the spread of weapons of mass destruction and monitoring the stability of regimes, such as Tunisia -- where protests toppled the government -- and Egypt, where protests were ongoing.
"The intelligence community has helped thwart many potentially devastating attacks," Clapper said. "One of the most recent was the cargo bomb plot this past October. ... We've apprehended numerous dangerous actors throughout the world and weakened much of al-Qaida's core capabilities, including its operations, training, and its propaganda."
Packages of plastic explosive were found on two separate cargo flights from Yemen to the United States last October. The explosives were removed outside the United States after intelligence from Saudi Arabia.
"We're especially focused on al-Qaida's resolve to target Americans for recruitment and to spawn affiliate groups around the world," Clapper said. "We also see disturbing instances of self-radicalization among our own citizens."
Counter-terrorism was especially important in Afghanistan and in Iraq, though the Iraq war is winding down, he said.
"Another major concern is the proliferation of weapons of mass destruction," he said. "The proliferation threat environment is a fluid, borderless arena that reflects the broader global reality of an increasingly free movement of people, goods and information. ... It allows the materials, technologies and know-how related to chemical, biological, radiological and nuclear weapons, as well as missile delivery systems, to be shared with ease and speed."
Clapper said he would discuss Iran in closed session. U.S. officials accuse Iran of trying to develop a nuclear weapons capability.
Celebrity Families of 2014 [PHOTOS]