Uefa president Aleksander Ceferin says the current football season could be lost if it cannot be restarted by the end of June.
Most leagues in Europe are suspended because of the coronavirus pandemic, with this summer's Euro 2020 tournament postponed for another year.
Ceferin says seasons could be finished behind closed doors.
"If we don't succeed in restarting, the season will probably be lost," the Slovenian said.
He told Italian newspaper La Repubblica: "There is a plan A, B and C.
"The three options are to start again in mid-May, in June or at the end of June.
"There is also the possibility of starting again at the beginning of the next [season], starting the following one later. We will see the best solution for leagues and clubs."
As it stands there are nine games to be completed by the majority of Premier League clubs, and up to 12 in the Football League.
All football in England is suspended until at least 30 April.
- Premier League, EFL & PFA say 'difficult decisions' to come for clubs
- What next for football as cracks begin to appear?
Ceferin says that playing remaining games behind closed doors would have to be an option across Europe.
"It's hard for me to imagine all the matches behind closed doors, but we still don't know whether we'll resume, with or without spectators," he said.
"If there was no alternative, it would be better to finish the championships."