"It has always been my intention to serve one term and after we (Bush and Powell) had a chance to have fulsome discussion on it, we came to the mutual agreement that it would be appropriate for me to leave at this time," Powell told reporters.
He said he would stay at the post for "a number of weeks" until a replacement is found. Possible names that have been floated include national security adviser Condoleezza Rice, U.N. Ambassador John Danforth and former Iraq administrator Paul Bremer.
In his resignation letter, dated Friday, Powell said: "As we have discussed in recent months, I believe that now the election is over, the time has come for me to step down as secretary of state and return to private life."
Powell had made no secret of his desire to leave the post after four years though publicly he maintained, "I serve at the pleasure of the president."
The secretary is the third Cabinet-level official to leave since the Nov. 2 election. Attorney General John Ashcroft and Commerce Secretary Don Evans resigned last week. Other resignations announced Monday were Secretaries Ann Veneman of Agriculture, Rod Paige of Education and Spencer Abraham of Energy.