The UK is facing an exit bill of up to €58bn
European Commission President, Jean Claude Juncker, has said that he views the UK's EU exit as a "failure and a tragedy."
"I am everything but in a hostile mood with Britain. Britain is part of Europe, and I hope to have a friendly relationship with the UK over the next decades," he said in an interview with the the BBC.
Mr Juncker said he fears that if three or more countries followed the UK the Union would collapse, but he does not believe that this will happen.
It remains unclear how costly the UK's exit fee will be - it has been reported that estimations from EU officials have set the bill at close to £50bn (€58bn).
Mr Juncker said that final number is yet to be "scientifically calculated."
"The British government and parliament took on certain commitments as EU members and they must be honoured. This isn't a punishment or sanctions against the UK," he added.
The Luxamborgian told the British broadcaster that the rights of EU citizens to remain in the UK is one area where the EU's negotiating team will accept no compromises during Brexit talks.
He is in Rome to attend EU's 60th-anniversary celebrations which EU leaders will attend tomorrow. British PM Theresa May will not travel to Italy.