UEFA president Aleksander Ceferin is confident the postponed Euro 2020 tournament will go ahead next year but admitted it could be staged in fewer than the planned 12 countries.
The 24-team tournament was delayed by a year due to the coronavirus pandemic, but a new surge of coronavirus infections across Europe has raised doubts over whether it can be played in the rescheduled slot between June 11 and July 11, 2021.
Wembley Stadium is due to host six matches - including two semi-finals and the final - while the pan-European format is also set to see matches held in Scotland and Ireland.
"We are always concerned about the situation (but) we are absolutely sure that the Euro will be played," Ceferin told the Spanish pay TV network Movistar+.
"The plan is that we do the Euro exactly as it is.
"But I have to say that, instead of 12 countries, we could do a Euro instead in 11, in eight, in five or in one country."
Ceferin added that it was too soon to say whether matches would be played without spectators, in full stadiums or with reduced capacities.
UEFA announced earlier this month they were to allow spectators back into matches in the Champions League and its other club and international competitions "at a maximum of 30 per cent" of capacity, subject to approval from national authorities.
Ceferin: UEFA considering week-long "final four" CL from 2024-25
Ceferin also said he liked the idea of finishing the Champions League with a week-long "final four" tournament and it was something to be considered for the next competition cycle, starting with the 2024-25 season.
Last season's competition finished with a "final eight" tournament with matches from the quarter-final onwards played over two weeks in Lisbon in a single-game knockout format, which saw Bayern Munich win the title.
It was initially intended as a one-off response to the coronavirus pandemic, which halted play for several months.
"The system last year was an interesting system and the feedback from the clubs that participated was that they were very happy with it," he said.
"A final eight is probably very hard to do calendar-wise, but for me … a final four, a week of football, might be a great event."