The New York Police Department’s top uniformed officer abruptly resigned, just days before he was to be promoted to become Commissioner William J. Bratton’s second-in-command, city officials said Friday.

The reason for the resignation of the officer, Philip Banks III, who held the position of chief of the department, was not immediately clear, the New York Times reports.

Chief Banks’s resignation was a surprise given its timing; it was only Tuesday when Mr. Bratton announced his intention to promote Chief Banks to be the first deputy commissioner.

Chief Banks, who is black, was to have replaced Rafael Pineiro, the highest-ranking Hispanic member of the department. Mr. Pineiro announced his retirement last month amid protests from some Hispanic police leaders who felt he had been forced out.

Both Chief Banks and Mr. Pineiro had been considered possible candidates to replace Mr. Bratton’s predecessor, Raymond W. Kelly, as police commissioner.