President Bush will name Bernard Kerik, a plain-spoken career police officer who headed the New York City Police Department during the Sept. 11 attacks, as secretary of the Department of Homeland Security, senior administration officials said today.

Kerik, who spent 4½ months in Iraq in an initial U.S.-led effort to rebuild the police force there after the fall of Saddam Hussein, would take over a department that was created just two years ago from 22 agencies with vastly different missions.

Kerik would replace Tom Ridge, the first head of the department, who announced his resignation Tuesday.

Also today, Bush nominated Mike O. Johanns, a two-term Republican governor of Nebraska, to be the next Agriculture secretary. If confirmed by the Senate, Johanns, 54, would succeed Ann M. Veneman, a Californian.

Since Bush was reelected a month ago, seven out of his 15 Cabinet secretaries have announced their resignations, and more are expected in the coming days and weeks, administration officials said. Replacements have been announced for five of those positions.

Bush is expected to formally announce Kerik's nomination Friday.

Confirmation hearings in the Senate for Bush's nominees, including Condoleezza Rice, nominated to be secretary of State, are not expected to begin until next year.

Nonetheless, "the president obviously would like to have his new team in place and ready to go as soon as possible," one official said.

In a brief ceremony in the White House Roosevelt Room today, Bush said of Johanns: "As the son of Iowa dairy farmers, he grew up close to the land. He will bring to this position a lifetime of involvement in agriculture and a long record of a faithful friend to America's farmers and ranchers."

Two years ago, Johanns became the first Republican to be reelected governor of Nebraska in almost a half-century. During his tenure, he traveled widely around the world to promote Nebraska farm products.

As governor, he supported spending for special education, opposed pay raises for public officials, vetoed a moratorium on the death penalty and, in a move that earned him the support of many unions in the state, supported a bilingual, meatpacking workers bill of rights, according to the Almanac of American Politics.

Johanns attended St. Mary's College in Minnesota and earned a law degree at Creighton University in Nebraska. He began his public service career in 1982 when he was elected to the Lancaster County Board of Commissioners. In 1989, he became a Lincoln city councilman and was elected mayor in 1991. Johanns was a Democrat until 1988.

Bush and Johanns have known one another for about a decade. Bush was elected Texas governor in 1994; Johanns was elected four years later.

The president said of Veneman, who was the first woman to head the Agriculture Department: "She has earned the trust of farmers and ranchers across America, and the whole nation has benefited from her service."

Bush added: "I chose Ann Veneman for her great expertise, her sound judgment and her bipartisan spirit, and she has displayed those qualities every day of her tenure. Ann has also carried out her duties while facing serious illness, and for that she has earned my increased admiration and the respect of her fellow citizens. I'm proud to know her, and I thank her for serving our country."

In 2002, Veneman received treatment after she was diagnosed with an early form of breast cancer.