The schedule announcement comes amid fears that the coronavirus outbreak, labelled a pandemic by the WHO on Wednesday, could have a major impact on the Games.
Games could still go ahead with mass athlete participation, but only if they were vaccinated.
The Tokyo Olympics had originally been scheduled for 2020 but were postponed by a year because of the pandemic.
Japanese Prime Minister Yoshihide Suga said on Thursday the Olympic torch relay scheduled in the city of Osaka has been cancelled amid a resurgence in COVID-19 cases.
Koike, speaking at the Foreign Correspondents' Club of Japan, said organisers were still hopeful venues could be filled with spectators when the Olympics begin in July.
Games should go ahead to demonstrate to the world what can be achieved with the right plan and measures.
Japan has extended a state of emergency in Tokyo and three other areas until the end of May and is struggling to contain a surge in COVID-19 cases
Tokyo 2020 Olympics chief Yoshiro Mori attended a meeting on March 10 that included the deputy head of the Japanese Olympic Committee (JOC) who tested positive for the new coronavirus this week, officials said. Mori, 82, has not been tested because he has no symptoms of the virus and does not meet testing requirements, an official from Mori's office said. Chief Cabinet Secretary Yoshihide Suga told reporters Prime Minister Shinzo Abe met Mori on March 16, without providing details.
Former Japanese Prime Minister Shinzo Abe collapsed in the western Japan city of Nara on Friday after being attacked by an unidentified man and gunshots were heard in the vicinity, local media reported adding that police has seized the attacker.
Two days after being named in Australia's Olympic tennis team, Nick Kyrgios said he is "tossing up options" and may opt out of the Tokyo Games due to COVID-19 restrictions.
Japan has largely avoided the kind of explosive coronavirus outbreaks that have devastated other countries
Towns and cities lined up to host Olympic training or events have increasingly expressed resistance
Japan's Naomi Osaka said on Sunday that while she has spent her entire life waiting to compete at the Olympics, the risks of holding the Tokyo Games amid the raging COVID-19 pandemic should continue to be carefully discussed.
US Vice President Kamala Harris would host a separate meeting with the prime ministers of three Quad countries -- India, Australia and Japan -- at the White House to discuss with them the important factors for democracies to go forward, officials said.
In a statement just before leaving for the US, Modi said he will conclude his visit with an address at the United Nations General Assembly focusing on the pressing global challenges including the COVID-19 pandemic, the need to combat terrorism, climate change and other important issues.
Ahead of the Quad summit on Friday, China said exchanges and cooperation between countries should contribute to mutual understanding rather than "targeting" a third party and refrain from "pursuing exclusive blocs".
"Relevant countries should abandon the obsolete Cold War mentality and narrow-minded geopolitical rivalry concept and view correctly and respect people's aspiration in the region and do more things conducive to regional solidarity and cooperation," Chinese foreign ministry spokesman Zhao Lijian said.
Union Sports Minister Kiren Rijiju had also said that Olympic-bound athletes will be given priority in the vaccination.
Here's what you need to know about the Tokyo Games
Japanese Prime Minister Yoshihide Suga reiterated on Thursday his intention to hold the Games.
A jump in infections has stoked alarm amid a shortage of medical staff and hospital beds in some areas of Tokyo
Prime Minister Narendra Modi on Thursday is scheduled to have as many as eight meetings, including with Vice President Kamala Harris, on the first working day of his current US trip.
Japan's top government spokesman said on Thursday that Tokyo's campaign to host the 2020 Olympics had been clean.
Half of the Japanese public think the 2020 Olympics will take place this summer, a survey by the Yomiuri daily newspaper showed on Monday, despite most people opposing holding the Games during the COVID-19 pandemic.
The quake struck near Kumamoto city on the island of Kyushu at a depth of 11 kilometres, the Japan Meteorological Agency said, adding that there was no tsunami risk.
'This also weighed on us, it weighed on me. But in order to arrive at this day today we had to give confidence, had to show a way out of this crisis'.
There is nothing to be worried about as bilateral ties are robust with solid foundations. Both are on the same page on the economic and defence/security ties bilaterally and globally and that shall continue irrespective of change in political dispensation in either country, points out Dr Rajaram Panda.
She added that Suga had encouraged her to make the Games successful but declined to say anything further until after a Tokyo 2020 executive board meeting later in the day, when an official announcement on the post was likely to be made.
According to the tentative plan, September 23-24 is being worked as the expected dates for Modi's US visit.
The International Olympic Committee and the Japanese government agreed last month to postpone the Games because of the global coronavirus outbreak. The costs of rearranging the Games and who will pay them have yet to be clarified by either the IOC or the Japanese government.
Organisers have already banned overseas spectators and set a cap on domestic spectators at 50 per cent of capacity
Another downgrade for Tokyo Olympics that have their pomp and public spectacle overshadowed by COVID-19
On Thursday, the prime minister is scheduled to hold one-on-one meetings with top five American CEOs. Two of them are Indian Americans -- Shantanu Narayen from Adobe and Vivek Lall from General Atomics. The three others are Cristiano E Amon from Qualcomm, Mark Widmar from First Solar, and Stephen A Schwarzman from Blackstone.
Japan's Asahi Shimbun, an official partner of the Tokyo 2020 Olympics, called for the Summer Games to be cancelled in an editorial
'If the Olympics were to spread infection, then what are the Olympics for?'
'Risk for the other residents of Olympic village and risk for the Japanese people is zero'
Prime Minister Narendra Modi on Tuesday gifted a Gond art painting, a specimen of Sanjhi art form and a wooden hand-carved box to his fellow Quad leaders from Australia, the US and Japan, sources said.
Japan has been less severely hit by the coronavirus pandemic than many other advanced economies, but a recent surge in cases spurred it to close its borders to non-resident foreigners and declare a state of emergency in Tokyo and major cities.
A video posted by the IS warns that Kenji Goto will be executed within 24 hours.
Japan is not making any preparations to postpone the 2020 Olympics, the government's top spokesman said on Wednesday, stressing Tokyo's resolve to host the event as scheduled despite the global spread of coronavirus.