International Olympic Committee vice-president John Coates arrived in Japan on Tuesday, as organisers ramp up final preparations with just over five weeks until the pandemic-postponed Games open.
Ahead of his arrival, several dozen people protested against the Games in Tokyo, though recent opinion polls suggest public opposition may be weakening.
Later Tuesday, organisers will release the final version of their virus countermeasures for athletes in a so-called "playbook" that they say will keep the event safe.
They have already announced measures including daily testing for athletes and GPS tracking of journalists coming from abroad, in an attempt to reassure a sceptical public.
National polls have regularly shown most people in Japan oppose holding the Games this summer — preferring either a postponement or cancellation.
But with the first foreign athletes already in the country and Olympic officials arriving, there is some evidence that opposition may be declining.
A survey in early June found half of the Japanese public back holding the Games, and a new poll published late Monday showed 64 percent now support it going ahead.
The new survey by national broadcaster NHK found 31 percent of respondents want the Games cancelled, down from 49 percent in May.
In all, 64 percent said they want the Games to go ahead — including 29 percent who favour a ban on spectators, 32 percent who want limited spectators and three percent who want no restrictions on fans.
The poll did not give the option of postponement, which organisers have ruled out.
Coates will be in quarantine for three days, according to local media, and subject to some restrictions on his movement after that.
Japan's mandatory 14-day quarantine for overseas arrivals is being relaxed for Olympic participants.
But organisers insist that Tokyo 2020 will be safe, with around 80 percent of those staying at the Olympic Village expected to be vaccinated, and rules preventing athletes from contact with Japan's public.
Overseas fans have already been barred from the Games, with a decision on how many domestic spectators will be allowed expected in late June.
The ruling will come after a virus state of emergency in Tokyo and other parts of the country is lifted on June 20.
The current measures largely involve a ban on the sale of alcohol at restaurants and bars, which must also close by 8pm.
Kyodo news agency reported late Monday that the government could keep some restrictions in place in Tokyo during the Games, potentially limiting the number of spectators who could attend.
Japan has seen a smaller outbreak than many countries, with just over 14,000 deaths, but Prime Minister Yoshihide Suga's government has come under fire for its response.
On Tuesday, opposition parties filed a motion of no confidence, but it is expected to fail given the government's large majority.
