This year's delayed London Marathon may now be restricted to elite runners only, race organiser Hugh Brasher has said.
However, he added this was just one of "ten scenarios" currently being considered by his team.
The 2020 edition of the race through the British capital was meant to take place on Sunday but has been postponed until October 4 because of the coronavirus outbreak.
But with no certainty as to when British government lockdown restrictions banning mass gatherings will be lifted, a race that featured nearly 43,000 runners last year may now follow the lead of last month's Tokyo Marathon, which went ahead with elite runners only.
Distance greats Eliud Kipchoge and Kenenisa Bekele are meant to compete in the elite men's race at this year's London Marathon and Brasher told the BBC: "We hope we can welcome them back in October but at this stage we just don't know what is going to happen.
"We have to look at it in totality, with three quarters of a million spectators, the medical side, the charities.
"We are looking at probably 10 scenarios, and they are changing all the time."
The Berlin Marathon, along with London one of the sport's six 'majors' will not go ahead as planned on September 27 after Germany extended a ban on large-scale gatherings until October 24.
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