Organizers of the 2020 Olympic Games in Tokyo admitted Thursday that the threat posed by extreme weather was a "major issue" as they updated National Olympic Committees on their preparations in Japan's capital.

"We observed unprecedented heat and typhoons last summer, and Tokyo 2020 considers those as major issues," Tokyo 2020 director general Toshiro Muto said at the general assembly of the Association of National Olympic Committees taking place at a hotel in Tokyo.

Japan was hit by a record heatwave that killed 96 people in Tokyo alone in July, while other parts of the country were devastated by typhoons and floods this year.

Muto said an "adverse weather issue resolution group" has been set up with the International Olympic Committee "to respond to various adverse weather conditions, including heat, heavy rain and typhoons," and that data from last summer's weather conditions would be provided to NOCs.

(Women walk past Japan's under-construction new National Stadium, the main venue for the 2020 Summer Olympics amid a July heatwave)

In his keynote speech following Muto, IOC President Thomas Bach again heaped praise on Tokyo's preparations but admitted the heat issue and transportation posed challenges, before saying "for everything there are solutions already under way."

The fact that the games will be staged between July 24 and Aug. 9 has caused alarm among some health officials, who fear for the safety of competitors, spectators and workers.

A record high of 41.1 C was registered in Kumagaya, near Tokyo, on July 23 this year, prompting the weather agency to call the heatwave "a natural disaster."

Fiji's Robin Mitchell, who has assumed temporary leadership of ANOC, told a press conference after the closure of the general assembly he hopes to reach solutions about the heat after listening to the ideas of stakeholders, including sport federations and broadcasters, at next week's Coordination Commission meeting.

Earlier this month it was revealed that organizers hope to have the marathon events start one hour earlier at 6 a.m. to avoid the heat.

On transportation, Muto told the ANOC general assembly that Tokyo 2020's plan was "very unique with venues being spread across the city and adjacent prefectures," and that due to traffic conditions in Tokyo "priority lanes" for Olympic vehicles will be used more than "dedicated lanes."

He also presented an update on water quality at Odaiba Marine Park, the venue for triathlon and marathon swimming, where a survey last year found E. coli bacteria at concentrations up to 21 times the level permitted by the International Triathlon Union.

Muto said tests last summer confirmed the effectiveness of underwater screens, with last month's results showing quality was within the governing body's standards, while pledging to carry out further tests to ensure water quality.

ANOC delegates will tour Odaiba Marine Park on Friday after visiting the Olympic and Paralympic villages, as well as other Tokyo 2020 venues in the Tokyo Bay area.

Later in the day, the IOC told the general assembly that it was able to trim about $4.3 billion (490 billion yen) from the planned cost of hosting the 2020 Games. It reviewed the use of existing infrastructure and shortening the period of borrowing venues as part of a set of measures collectively known as "The New Norm."

The New Norm, passed by the IOC this year, encourages host cities to plan the games in line with their own long-term development needs, with a focus on sustainability and driving down costs.

Approximately 1,400 representatives from all 206 NOCs, the IOC, international sports federations and Games organizing committees have assembled in Tokyo for the annual two-day event amid an intense period of Olympic activity in the capital.

In Wednesday's morning session, Sheikh Ahmad Al-Fahad Al-Sabah reiterated his decision to temporarily step down as ANOC president amid allegations in Switzerland of forgery. Last week, the Kuwaiti suspended himself from his 26-year IOC membership.

Mitchell took the role of interim president after being elected senior vice president.

The assembly will be followed by an IOC executive board meeting on Friday and Saturday, before the IOC Coordination Commission reviews Tokyo 2020's progress from Monday through Wednesday.

The 2019 assembly will take place in San Diego, while the 2020 edition will be cohosted by South and North Korea in Seoul.