Kerik, who helped rally New York City's police force and its citizens following the Sept. 11 terrorist attacks, is the latest Bush appointee to his much-shifting Cabinet.
"Bernie Kerik is one of the most accomplished and effective leaders of law enforcement in America," Bush said in his formal nomination Friday. "In every position he has demonstrated a deep commitment to justice, a heart for the innocent and a record of great success."
Amid the major changes, Mr. Bush has asked Defense Secretary Donald Rumsfeld to stay on as a member of the his Cabinet, according to a senior administration official.
The official said Rumsfeld agreed to remain in his job.
Bush and Rumsfeld decided on the secretary's future during an Oval Office meeting. Whether or not Rumsfeld remained had been the last big question mark about Bush's Cabinet for his second term, since that of who would replace Homeland Security secretary Tom Ridge.
Mr. Bush laid out his answer to that question at a White House bridfing Friday.
"[Kerik} understands the duties that came to America on Sept. 11. The resolve he felt that morning will guide him every day on his job." Mr. Bush said.
"I know what is at stake," Kerik said.
He said that what he witnessed in the days after the attacks would be etched in his mind if he were confirmed by the Senate to lead the department.
"Both the memory of those courageous souls and the horrors I saw inflicted upon our proud nation will serve as permanent reminders of the awesome responsibility you place in my charge," Kerik said.
In other Bush Cabinet news,submitted his resignation Friday, becoming the eighth member of Mr. Bush's 15-member Cabinet to step down as part of a major administration reshuffling ahead of the president's second term.
A day earlier, Mr. Bush announced that he had chosenas secretary of Agriculture to oversee the nation's farm and food programs. He will replace Ann Veneman.
Also Thursday, U.N. Ambassador, just five months after taking the post. He had been mentioned as a successor to Secretary of State Colin Powell, but Mr. Bush picked Condoleezza Rice instead. Danforth says he plans to retire.
The 49-year-old Kerik's path to the top homeland security position was unconventional, but he campaigned arduously for Mr. Bush this year.
A military policeman in South Korea in the 1970s, Kerik's first anti-terrorism work was as a paid private security worker in Saudi Arabia. He joined the New York Police Department in 1986, first walking a beat in Times Square when it was still a haven for small-time hustlers.
He eventually was tapped to lead the city's corrections department, and was appointed police commissioner in 2000.
It was in that position that he became known to the rest of the country, supervising the NYPD's response to the Sept. 11, 2001, terror attacks, often at the side of then-mayor Rudolph Giuliani. Kerik helped repair a department that lost 23 members and became a steady hand for a population deeply shaken by the attacks.
Most recently, he has been a consultant for Giuliani Partners, working to rebuild Baghdad's police force.
"Coming from New York, Bernie Kerik knows the great needs and challenges this country faces in homeland security," said Sen. Charles Schumer, D-N.Y, who, along with his Senate colleagues, will need to confirm Kerik to his new post. "He has a strong law enforcement background and I believe will do an excellent job in fighting for the resources and focus that homeland security needs and deserves in our post-9/11 world."
Kerik inherits a new and sprawling bureaucracy. The creation of the department in 2003 combined 22 disparate federal agencies with more than 180,000 employees and a combined budget of $36 billion. The organization is still learning to work together and faces criticism over aspects from the coordination of finances to computer systems.
Mr. Bush initially opposed the creation of the department, but changed his tune as its support on Capitol Hill grew.