The International Olympic Committee wants to move the Tokyo Games marathons 800 kilometers (500 miles) north to avoid the searing heat in the city.
The IOC said in a statement that the new plan to stage the marathons and race walking events in Sapporo, the host city of the 1972 Winter Olympics, "will mean significantly lower temperatures for the athletes."
President of Tokyo 2020 Yoshiro Mori said that organisers want more time to discuss the move, but admitted that they would have to accept the IOC's decision.
"If the IOC and the International Association of Athletics Federations (IAAF) support it how can our organising committee tell them no," Mori told reporters on Thursday.
Forecast temperatures in Sapporo are "five to six degrees centigrade cooler during the day than in Tokyo."
An IOC panel assessing heat and weather issues for the July 24-Aug. 9 games "identified the marathon and race walk as the events that would put particular heat stress on the athletes."
High temperatures in Tokyo last summer led to the deaths of over 50 people, highlighting the health threat to athletes and fans at the Olympics next summer.
The marathons were due to start at 6 a.m. in Tokyo.
Marathons were run after midnight in 38 degrees C (100 degrees F) this month at the track and field world championships in Doha, Qatar.
Additional reporting from Reuters contributed to this report.