The European Union is warning Britain that any financial commitment it has taken on as a member "should be honored in full," even well after it leaves as a result of the Brexit negotiations.

Estimates have been made that the bill at the exit door could go as high as 60 billion euros ($64 billion).

"This will be an essential element of the negotiations on the orderly separation," EU Commission spokesman Margaritis Schinas said Tuesday.

Otherwise, he said, it would be like going to a pub with 27 friends, ordering a round and leaving while the party continues.

"You still need to pay for the round you ordered," Schinas said.