London Marathon organisers have "not given up hope" of holding the event in October, despite the ongoing coronavirus pandemic.
The 40th edition of the race was originally scheduled for 26 April but was pushed back to 4 October at the start of the outbreak.
Race director Hugh Brasher said he "hopes that the world will have found a way through coronavirus" by October.
There will be a further update on the event on 28 July.
It is the first time the race, first run in 1981, has been postponed.
"Whatever decision we take will be in line with our values and with the responsibility we have," Brasher wrote.
"Focus on your own health and the health of those around you. Focus on running and exercise."
Nearly 43,000 runners competed in the 2019 edition, with £66.4m raised for charity. Eliud Kipchoge claimed a record fourth title in the men's elite race, while Brigid Kosgei took the women's title.
Brasher had previously suggested this year's event could take place with only elite athletes.
"We still don't know whether we will be able run together, walk together and be together on that journey of 26.2 miles on 4 October," Brasher added.
"Almost every day we hear hopeful news from other countries and we hear tales of despair.
"However, what we do know is that we have hope, desire and ingenuity."
The Great North Run, also in its 40th year, was cancelled on Monday.
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