TOKYO (AFP) - The Tokyo Olympics will begin on July 23 next year, organisers said on Monday (March 30), after the coronavirus forced the historic decision to postpone the Games until 2021.

The announcement comes less than a week after the organisers were forced to delay the Games under heavy pressure from athletes and sports federations as the global pandemic worsened.

"The Olympics will be held from July 23 to August 8, 2021. The Paralympics will be held from August 24 to September 5," Tokyo 2020 chief Yoshiro Mori told reporters at a hastily arranged evening news conference.

Only hours earlier, Mori had said he expected a decision from the International Olympic Committee (IOC) during the course of the week.

But on Monday evening, he said an emergency teleconference had been held with the IOC and the date finalised.

"We agreed that the timing of the event will be in summer as originally planned, considering the coronavirus... and a certain amount of time needed for preparations, selection and qualification of athletes," he added.

In a statement, the IOC said the new dates would give health authorities and organisers "the maximum time to deal with the constantly changing landscape and the disruption caused by the Covid-19 pandemic".

The decision would also cause "minimum" disruption to the international sports calendar, the body said.

The Tokyo 2020 Olympics were due to open on July 24 this year and run for 16 days, but the coronavirus pandemic forced the first peace-time postponement of the Games.

The IOC and Japan had for weeks insisted the show could go on but the rapid spread of Covid-19 prompted growing disquiet among athletes and sporting federations.

The Olympics was the highest-profile sporting casualty of the coronavirus that has wiped out fixtures worldwide and all but halted professional sport.

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There was some speculation that Japanese organisers could take advantage of the blank canvas to shift the Games to spring, avoiding the heat of the Tokyo summer that had been their main concern before coronavirus struck.

Due to the heat, the marathon has been moved to Sapporo, a city some 800 kilometres to the north of Tokyo where the weather is cooler even at the height of summer.

The postponement has handed organisers the "unprecedented" task of rearranging an event seven years in the making, and Tokyo 2020 chief executive Toshiro Muto has admitted the additional costs will be "massive".

According to the latest budget, the Games were due to cost US$12.6 billion (S$18 billion), shared between the organising committee, the government of Japan and Tokyo city.

However, that number is hotly contested with a much-publicised government audit suggesting the central government was spending several times that amount - on items organisers claim are only tangentially related to the Olympics.

The postponement affects every aspect of the organisation - hotels, ticketing, venues and transport being among the major headaches.

Hotels have had to cancel bookings, dealing them a bitter blow at a time when tourism is already being hammered by the coronavirus.

Some venues that had booked events years in advance will potentially have to scrap them to make way for the rescheduled Olympics and there is still uncertainty about whether ticket-holders will get refunded.

Another thorny issue is the athletes' village, which was due to be converted into luxury apartments after the Games, some of which have already found buyers.

The Japanese government had touted the Games as the "Recovery Olympics", designed to show how the country had bounced back from the 2011 triple disaster of the earthquake, tsunami and nuclear meltdown in the northeastern Fukushima region.

The Games are now being billed as the expression of humanity's triumph over the coronavirus.

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"Humankind currently finds itself in a dark tunnel," IOC chief Thomas Bach said in Monday's statement announcing the new date.

"These Olympic Games Tokyo 2020 can be a light at the end of this tunnel."

Mori earlier warned that organisers were faced with an "unprecedented challenge".

"But I believe it is the mission of the Tokyo 2020 organising committee to hold the Olympics and Paralympics next year as a proof of mankind's victory against the virus," he said.