The IOC is to step-up its "scenario planning" for the Tokyo 2020 Games, including a possible postponement, it said after an emergency meeting on Sunday.

The IOC will hold detailed discussions that will include an option of putting back the 24 July start date due to the global coronavirus pandemic, but said a complete cancellation of the Games would not solve problems or help anybody.

"Therefore, cancellation is not on the agenda," the IOC said in a statement, adding that the discussions would be completed within the next four weeks.

The Olympics has never been postponed or cancelled during peacetime.

Under mounting pressure from athletes - Irish Olympic silver medallist Sonia O'Sullivan has called on the IOC to postpone this summer's Games - federations and national Olympic committees to postpone the Games, the IOC did a partial U-turn on Sunday after long insisting, with Tokyo organisers, that the Games would go ahead as planned.

The International Paralympic Committee, whose Tokyo Paralympics are set for 25 August to 6 September, said the IOC took the right decision under the circumstances.

"The next four weeks will provide time to see if the global health situation improves, while giving a window of opportunity to look into different scenarios should the dates of the Games need to be changed," IPC President Andrew Parsons said.

Nine-times Olympic gold medallist Carl Lewis has called for the 2020 season to be scrapped.

"Let's wipe the season clean, focus on the (2021) worlds and get it together," America's most decorated track and field athlete told Reuters in a telephone interview.

"It's going to hurt a lot, but wipe it clean."

With the uncertainty now of whether there will be a Games in 2020 and the tightening of people's movement by governments to try to control the virus, "we are in the twilight zone," Lewis said.

"I don't think the Olympics are going to happen, but, we have to prepare as we are going."

Opposition to holding the Games in July has risen sharply in the past 48 hours, with several major stakeholders such as U.S. Track and Field and UK Athletics along with several national Olympic committees, calling for a delay because of the pandemic.

They have raised several issues in the past week with the IOC, including athletes' inability to prepare due to restrictions caused by the virus and their overall safety.

Regarding the next steps in scenario planning, the IOC statement said: "These scenarios relate to modifying existing operational plans for the Games to go ahead on 24 July 2020, and also for changes to the start date of the Games.

"The IOC will... start detailed discussions to complete its assessment of the rapid development of the worldwide health situation and its impact on the Olympic Games, including the scenario of postponement.

"The IOC is confident that it will have finalised these discussions within the next four weeks."

In a letter addressed to athletes, IOC President Thomas Bach tried to explain the IOC's insistence in the past weeks to proceed as planned, saying moving the Games could not happen from one day to the next and many parts had to be looked at.

"I think I can feel with those among you who consider the situation to be unsatisfactory," Bach said.

"I know that this unprecedented situation leaves many of your questions open. I also know this rational approach may not be in line with the emotions many of you have to go through.

"A decision about a postponement today could not determine a new date for the Olympic Games because of the uncertain developments in both directions: an improvement... in a number of countries... or a deteriorating situation in other countries."