During a Tuesday speech in Denver, Napolitano said so-called "fusion centers," where federal, state and local law enforcement share information about possible plots, were instrumental in arresting a suspect in the attempted car bombing in Times Square and in foiling the attempt to bomb New York's subway system.

She was referring to the role of Colorado's fusion center, the Colorado Information Analysis Center in Lakewood, in the FBI's investigation of Najibullah Zazi, an Aurora airport-shuttle driver convicted in a 2009 plot to explode homemade bombs in the New York subway.

Napolitano said plots against the nation "increasingly involve American residents or American citizens" and that she's trying to distribute resources into local communities.

She was speaking to 1,000 law enforcement officers from across the country attending the National Fusion Center Conference at the Colorado Convention Center. The meeting's goal was improving training and information sharing among 72 state and urban fusion centers across the United States.

The centers are designed to gather information about terrorism and other threats and share it with agencies that need to know.