Mr. Bush chose retired Army Gen. Wayne Downing to be deputy national security adviser for combating terrorism, and Richard Clarke, who is already working on anti-terrorism at the White House, as special adviser for cyberspace security.
The president's new director of homeland security, Tom Ridge, Tuesday announced the appointments.
Ridge said defending America's computer infrastructure is crucial adding that if you shut it down, you "shut down America as we know it."
"Global terrorism poses a grave danger to the national security of the United States and to the safety of all Americans at home and abroad," the White House said.
Downing will be Bush's principal adviser on matters related to combating global terrorism, including "all efforts designed to detect, disrupt and destroy global terrorist organizations and those who support them," the White House said.
A career specialist in counter-terrorism, Downing wrote a highly critical official report on security lapses in the military after 19 U.S. troops were killed in the 1996 bombing of the Khobar Towers barracks in Saudi Arabia. He is a 34-year army veteran who has headed the Special Operations Command.
The report recommended the government regard terrorism as an "undeclared war against the United States."
Clarke will coordinate efforts to secure information systems, including telecommunications, banking and finance, transportation, energy, manufacturing, water, health and emergency services networks. He served at the State Department and National Security Council under presidents Reagan, Bush and Clinton.
In the event of a disruption, he will be the top coordinator for restoring critical systems.
Even before he was sworn in as the U.S. homeland security chief Monday, Ridge took a seat in the president's morning briefing by Federal Bureau of Investigation officials. Original plans for Vice President Dick Cheney to give Ridge the oath of office were scrapped for security reasons and Supreme Court Justice Clarence Thomas performed the duty; Cheney remained at an undisclosed location Monday morning.
Ridge, who resigned as Pennsylvania governor a few days ago, is now seated at the center of power in Washington. "The size and scope of this challenge are immense," Ridge said moments after he was sworn in.
His job, he said, is to close the gaps in the nation's current anti-terrorism efforts - gaps that permitted small cells of terrorists to murder thousands.
"The terrorists will not take away our way of life," Ridge said.
Ridge said his new task as one to "detect, prepare for, prevent, protect against, respond to and recover from terrorist attacks - an extraordinary mission but we will carry it out."
Mr. Bush gave Ridge a West Wing office just a few paces from his own, and a broad mission: Develop a "coordinated, integrated, national strategy to combt terrorism," White House spokesman Scott McClellan said.
Ridge was getting a staff of nearly 100, most of them currently working for the White House or other agencies, and a dozen employees of his own. He will report directly to the president, McClellan said.
Critics have questioned how much clout Ridge will have. Although the president was naming him to his Cabinet, Ridge is not one of the 14 Cabinet members installed under federal law, each with his own budget and authority. Each president may designate any number of other top advisers as "Cabinet level," and that is what the president did with Ridge.
"The mission is to develop a coordinated, integrated and comprehensive national strategy to safeguard America against terrorism and respond to any attack that may come," said White House spokesman Scott McClellan. "He will coordinate efforts throughout all level of government, federal state and local."
McClellan said Ridge will have "significant input into the budgets of agencies involved in homeland security," though his own budget will be part of the White House's. "Governor Ridge will have all the authority he needs to get things done."
A Homeland Security Council consisting of Mr. Bush, Cheney, Ridge and various agency heads will tackle domestic terrorism much as the National Security Council advises the president on international affairs.
The challenges Ridge faces are monumental by all accounts.
Despite heightened security in the wake of last month's attacks, particularly at U.S. airports, experts say the nation's borders remain porous in some places, and that it would be impossible to defend every potential target because there are so many.
Ridge will also face the daunting challenge of getting more than 40 agencies, including the FBI, CIA and dozens of state and local authorities, to cooperate and heed his command.
Key lawmakers are warning Ridge lacks the jurisdictional and budgetary powers to rein in fiercely independent agencies that have agendas of their own.
The White House insisted Ridge will have a strong voice in budgetary decisions to ensure each area of government takes homeland security into account.
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