Washington ? In a surprise move, former New York Police Commissioner Bernard Kerik abruptly withdrew his nomination as President Bush’s choice to be homeland security secretary Friday night, saying questions have arisen about the immigration status of a housekeeper and nanny he employed.

The decision caught the White House off guard and sent Bush in search of a new candidate to run the sprawling bureaucracy of more than 180,000 employees melded together from 22 disparate federal agencies in 2003 to guard the nation against terrorist attacks.

Kerik’s nomination had been widely praised by Democrats and Republicans alike. A former military man, he became widely known for his role in helping direct the emergency response to the Sept. 11 terrorist strikes against the Twin Towers.

Kerik informed Bush of his decision to withdraw in a telephone call. “I am convinced that, for personal reasons, moving forward would not be in the best interests of your administration, the Department of Homeland Security or the American people,” Kerik said in a letter to the president.

The White House said Bush accepted Kerik’s decision.

Kerik is not the first prominent official to fall victim to the “nanny problem.” Similar issues killed the nomination hopes of three candidates for top administration posts in the Clinton administration.

One administration official helping prepare Kerik for Senate confirmation, speaking on condition of anonymity, said Kerik’s unexpected decision shocked senior leaders at the Homeland Security Department. This official said Kerik still had not filled out all his ethics filings — which would detail his sources of income and financial liabilities — and said the FBI background investigation of Kerik was still incomplete.

But the only moderately troubling information uncovered about Kerik so far had been news that Kerik had earned $6.2 million by exercising stock options he received from Taser International, which did lucrative business with the Homeland Security Department, this official said.