Several major Japanese media sources report that Mori had told officials of his wish to step down, saying he intends to announce his resignation at a meeting of Games organisers on Friday.
Gaffe-prone Mori, an 83-year-old former prime minister, has come under increasing pressure after he said last week that women have trouble speaking concisely.
"When you increase the number of female executive members, if their speaking time isn't restricted to a certain extent, they have difficulty finishing, which is annoying," he reportedly told members of the Japanese Olympic Committee.
He then apologised for the sexist remarks, explaining that he "doesn't speak to women much".
Sponsors get the jitters
Politicians and sports stars were quick to condemn Mori's comments, which heavyweight sponsors have also said run contrary to the Olympic spirit.
Games sponsor Toyota on Wednesday issued a statement by its president Akio Toyoda saying: "It's very regrettable that the comments made by the leader of the organising committee differ from the values that Toyota holds."
Replacement already on the sidelines
Officials are considering appointing former football player Saburo Kawabuchi as Mori's replacement as head of Tokyo 2020, broadcasters TBS and NTV reported.
Saburo Kawabuchi, former football association chair, may head Tokyo Olympic committee https://t.co/0gKwgFS4iu
— The Mainichi (Japan Daily News) (@themainichi) February 11, 2021
Kawabuchi is an 84-year-old long-time sports administrator who played a large part in popularising football in Japan in the 1990s, and is involved in the Games as the symbolic mayor of the Olympic Village.
Backlash forces IOC change of tone
Having initially said it considered the matter closed with Mori's apology, the International Olympic Committee branded his remarks "completely inappropriate" as the backlash grew.
At Friday's meeting, organised in the wake of the sexism row, Games officials will "express their opinions" on Mori's remarks and discuss "future gender equality initiatives of the Tokyo 2020 organising committee", it has said.
An online campaign calling for action against Mori has attracted more than 146,000 signatures, while tennis superstar Naomi Osaka slammed his comments as "ignorant".
Since Mori's remarks, around 400 Olympic and Paralympic volunteers have quit, according to Tokyo 2020, which has said the number includes withdrawals for all reasons.
