U.S. media reports say Secretary of Homeland Security Tom Ridge plans to announce his resignation Tuesday.
Political analysts say the move is not surprising, as Mr. Ridge had signaled he did not plan to stay for President Bush's second term.
President Bush named Mr. Ridge the nation's first homeland security adviser less than a month after the September 11th, 2001 terrorist attacks.
He became Secretary of Homeland Security when Congress established the agency as its own department overseeing the Coast Guard, the border patrol, immigration and other agencies.
There was no immediate word on whom President Bush might nominate to be Mr. Ridge's replacement.