The annual event, which is being staged in Qatar, is traditionally held at the end of the year and had been scheduled to begin next month.
However, FIFA said that is not feasible because of "the disruptive effect of the pandemic on the confederations' continental club championships that serve as a pathway for the event".
It will instead be staged from 1 February to 11 February.
European champion Bayern Munich and Al-Duhail, the 2019-2020 Qatar Stars League winner, are the only confirmed participants so far.
The 2021 tournament will be the last before the expanded competition, which is due to replace the Confederations Cup on the football calendar, is first held in China.
FIFA also confirmed the 2020 Under-20 and Under-17 Women's World Cups have been cancelled after stakeholders raised concerns about staging the tournaments.
The events had been postponed until early next year because of the impact of the pandemic.
FIFA said the 2020 hosts – Costa Rica for the Under-20 tournament and India for the Under-17s – will now have hosting rights moved to the 2022 competitions.