Brown said he could not "commit to the time and preparation that this job deserves and requires" due to "uncertainties around the direction of my professional future" after he was sacked by National Basketball Association (NBA) team the Philadelphia 76ers.

The 59-year-old American had been appointed head coach by Basketball Australia in November 2019 and was set to manage the team at Tokyo 2020 this year before the Games were postponed because of the coronavirus pandemic.

Basketball Australia chief executive Jerril Rechter said in August that he still expected Brown to coach the side at the Olympics, despite losing his job with the 76ers.

"While I have a deep and long-standing passion for Australian Basketball, I am currently unable to commit to coaching the Boomers at next year's Olympic Games," Brown said. 

"The uncertainties around the direction of my professional future unfortunately mean that I cannot commit to the time and preparation that this job deserves and requires. 

"The difficulties around traveling internationally with my family during the pandemic have also contributed to my decision.

"It is important for me to give Basketball Australia, the coach, and players, the necessary time for a full and thorough Olympic Games preparation in the event that the Games do proceed."

Brown was fired by the 76ers after they were swept 4-0 by the Boston Celtics in the first round of the NBA play-offs.

He had coached the team for the past seven seasons.

Brown was reappointed as the head coach of Australia's men's basketball team last year, replacing Andrej Lemanis.

He previously coached Australia between 2009 and 2012, which included the 2010 World Championships in Turkey and an Olympic quarter-final appearance at London 2012.

"Basketball Australia is naturally disappointed that Brett is no longer able to commit to being the Boomers head coach for the delayed Tokyo Olympics but we fully understand Brett's situation, and appreciate his candidness when informing us of the decision," Rechter said.

"The COVID-19 pandemic is creating a challenging environment for all sports in which to operate. 

"The Tokyo Olympics is an important event for Basketball Australia and our male athletes, as collectively we believe the Boomers have an excellent opportunity to claim their first ever Olympic medal.

"Basketball Australia will commence recruitment for this position in the coming period, with details of the process to be released in due course."