Organizers of the Tokyo 2020 Olympics have decided to move up the start time of the men's and women's marathons from 7 a.m. to 6 a.m. over concerns of extreme heat, an informed source said Monday.

A 5:30 a.m. start had also been proposed, but was rejected due to the difficulties spectators would have getting to the marathon route in time and the negative effect it would have on television broadcasts.

On Saturday, while the International Olympic Committee's Executive Board met in Tokyo, a panel formed to propose solutions to the issues weather may pose for the summer games suggested 5:30 a.m. starts. One official said it was necessary to start no later than 6 a.m.

Both the international and domestic sanctioning bodies for athletics wanted to start before six, but the Tokyo 2020 organizers settled on 6 a.m., and that will be put forward once the International Association of Athletics Associations signs off on it.

There had been some desire to have the men's 50-kilometer race walk start between 3 and 4 a.m., but that event's start time will possibly be set at 5:30 a.m.

The marathons were originally slated to start at 7:30 a.m., but were moved a half-hour earlier to 7:00 a.m. after IOC approval in July. But cries for more aggressive measures became louder as a heat wave brought record temperatures to Japan in August, raising safety concerns for athletes, spectators and staff during the 2020 Olympics.

The women's marathon is scheduled for Aug. 2, with the men's to be held on Aug. 9, the final day of the summer games. This summer's Asian Games marathon in Jakarta also started at 6 a.m.