WASHINGTON - The government will react less to smaller terrorist threats and focus more on preventing attacks that could kill large numbers of people and ruin the economony, according to the nation's Homeland Security chief.

Michael Chertoff said the shift in strategy is part of a sweeping departmental reorganization he will announce today. The aim is to put a priority on stopping catastrophic nuclear, chemical or biological attacks - - or at the least, minimizing their damage, he said in an interview with USA TODAY.

He announces his plan less than a week after bombings in London prompted the Bush administration to raise the terrorist threat level to "high" for the nation's mass transit systems.

Chertoff did not specify the kind of terror threat he would de-emphasize or how he proposes to shift resources. But he rejected recent calls by Sen. Charles Schumer, D-NY, and others in Congress for a sharp boost in spending to tighten rail security. He said government officials need to "keep our eye on the ball and focus on our priorities."

Chertoff said the public needs to be mindful that "we're going to have the issue of terrorism and these kinds of events for a very long time to come." He added, "We can't be complacent, but we also need to kind of build in a sense of stability and calmness, and not react or overreact to individual instances."

Chertoff, who took over in February as secretary for Homeland Security, said he looks forward to "finally getting control of the border in a way we haven't succeeded in doing" and improving passenger and cargo screening with the use of biometric IDs. He said he also is looking for better ways to distribute medicine if terrorists use radioactive or biological weapons.

Among Chertoff's other new ideas: