British expectations in its divorce proceedings from the European Union are "not realistic", Belgian prime minister Charles Michel has said.
He sent a clear warning that Britain will not escape a hefty bill for its momentous decision that has shaken the bloc.
Mr Michel said, in an interview with The Associated Press, that "those who think in Britain they can push the Brexit button and not have a bill to pay are seriously mistaken".
Both sides have sparred over the negotiations, which are to start after the June 8 General Election. Some question what, if anything, Britain should pay for.
Estimates have ranged from 20 billion to 60 billion euro (£17 billion to £51 billion). The Financial Times upped the figure to as much as 100 billion euro (£85 billion), a figure Britain has flatly rejected.
"In Britain ever more, they will realise that Brexit, well, has consequences - economic, commercial, partnerships," Mr Michel said.
"Perhaps during the referendum the impression was given that once the Brexit button was pushed everything would take care of itself easily.
"Well, that is not true. When you push that Brexit button, there are consequences, there is a bill to pay."
The 27 other EU nations have shown a united front and Mr Michel epitomised the view that the negotiations should be done on the EU's terms, not Britain's.
He said it was not up to Prime Minister Theresa May to impose her negotiating strategy. She has been seeking parallel talks on unwinding EU membership while negotiating a future relationship and trade deal.
"That's not realistic," Mr Michel said. "We are splitting, like a divorce. You need to address the material issues, financial, who gets the kids, transitional measures."
"It is only afterward that we can look at the future. You have to turn a page before you start writing the next one. And it is up to Mrs May to understand this."
Under the EU blueprint, negotiations would first centre on finding a deal for citizens living and working in each other's nations, settle Britain's financial obligations and the border between Ireland and Northern Ireland.
If sufficient progress is made, only then would the EU be willing to open talks about a future relationship.
EU Council president Donald Tusk said this could come as soon as autumn, but Mr Michel said that was an extremely tight deadline.
He said: "It would be smart to immediately put the difficult questions on the table.
"Otherwise we run the risk of negotiating on the easy questions for a year or 18 months and as the two-year deadline draws near have an explosion in talks since the tough questions would come up too late."
Mr Michel said a rift still exists in Britain itself.
"It is also complex in a political sense since there is, in Britain, not a monolithic opinion. We see there are lively, very rough debates - in parliament, within public opinion, debates on the situation in Scotland."
Mrs May accused EU officials this week of trying to influence the election, deliberately timing comments and moves to coincide with the campaign.
"It is clear that the situation in Britain over the coming months will not be resembling one long, tranquil river. There will perhaps be ups and downs in Britain," Mr Michel said.