New York ? Three weeks before its next round of coaching hirings, the NFL wants to make sure its teams adhere to the minority hiring guidelines it set last season.

In a memo released Tuesday, the league’s diversity committee reiterated that all teams must interview at least one minority candidate for coaching vacancies, and banned telephone interviews of candidates. It also mandated that owners get involved in the final interviews for coaches.

“Clubs should make certain that they identify a deep and diverse … pool of head coaching candidates,” said the memo from the committee, headed by Pittsburgh owner Dan Rooney.

“As part of this effort, clubs should be sure that they are knowledgeable about potential minority candidates for the head coaching vacancy both within and outside their own organization.”

There are three black coaches in the NFL: Tony Dungy of Indianapolis, Herman Edwards of the New York Jets and first-year coach Marvin Lewis of Cincinnati. There have been six since Art Shell became the first of the modern era in 1989 with Oakland.

There are expected to be six to 10 head coaching vacancies this season and there are several black candidates who could land jobs after the regular season at the end of this month.

Among them are former Minnesota coach Dennis Green, offensive coordinator Maurice Carthon of Dallas and defensive coordinator Lovie Smith of St. Louis.