Aleksander Ceferin has warned clubs clinging to the Super League dream that they could face bans from the Champions League.
The UEFA president has been speaking with AP with Real Madrid, Barcelona, Juventus and AC Milan yet to formally disavow themselves from the Super League.
All six Premier League clubs named as founders on Sunday night had dropped out within 48-hours. Fan pressure had been brought to bear, but it seems influences from the Kremlin and Abu Dhabi were more influential.
Real Madrid president Florentino Perez remains a vocal Super League proponent, while his Barcelona counterpart Joan Laporta still insists a Super League - in some form - is "absolutely necessary".
AC Milan released a statement regarding the now toxic nature of the proposal, but didn't formally back out. While Juventus president Andrea Agnelli claims the current proposal is not workable, but remains married to the idea.
"It’s crystal clear that the clubs will have to decide if they are Super League or they are a European club," Ceferin told AP.
"If they say we are a Super League, then they don’t play Champions League, of course ... and if they are ready to do that, they can play in their own competition.”
Financiers JP Morgan distanced themselves from the Super League on Friday, having originally agreed to fund the project to the tune of €3.5billion.
Clubs are still set to owe the company millions in break fees.
"We still are waiting for legal expertise and then we will say," Ceferin said regarding UEFA's next steps, "But everybody faces consequences for their decisions and they know that.
“For me, it’s a very different situation between the clubs that admitted their mistake and said, ‘We will leave the project.’
"The others mainly know I would say that this project is dead, but they don’t want to believe it, probably.”