CHICAGO (SI.com) -- Bud Selig plans to step down as commissioner of Major League Baseball when his current contract expires on Dec. 31, 2012, according to a report in the Chicago Tribune.

The 75-year-old Selig, who has been commissioner since 1998, declined a request from a group of five MLB owners to stay on beyond that time, the newspaper reported Saturday, citing unnamed sources. He reportedly told the owners he would step aside then because he had other things he wanted to do, such as teaching and writing a book.

If he stays on till 2012, Selig will have been baseball's top boss for 20 years, including six years as interim commissioner from 1992 to 1998.

His time in office has included such events as the players' strike in 1994, the introducion of the wild-card system and interleague play, and investigations into steroid use. He received a three-year contract extension last year.

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