European Commission President Jean-Claude Juncker has said he hopes that the UK will rejoin the European Union at some point in future.
Mr Juncker, the most senior official in Brussels, said he did not like Brexit because he wanted “to be in the same boat as the British”.
“The day will come when the British will re-enter the boat, I hope,” he said following an EU summit.
Former UKIP leader Nigel Farage said: “The ship will have sunk by then.”
The UK is expected to trigger the formal Brexit process this month, beginning a two-year negotiation process of withdrawal.
German Chancellor Angela Merkel said if the UK invoked Article 50 next week, an extraordinary meeting of the other 27 EU states would be held on 6 April.
“We are well prepared and we shall wait with interest,” she said.
Prime Minister Theresa May attended the Brussels meeting on Thursday, but left early as the remaining 27 members stayed on to discuss the future of the European Union.
She told reporters before leaving: “At this summit we’ve shown once again how Britain will continue to play a leading role in Europe long after we have left the EU” – citing the examples of security cooperation and hosting a summit for the Western Balkans.
European Council President Donald Tusk said the EU would be ready to respond within two days of Mrs May triggering Brexit: “We are well prepared for the whole procedure and I have no doubt that we will be ready in 48 hours.”
Meanwhile the European Parliament’s chief Brexit negotiator, Guy Verhofstadt has said he would like a “special arrangement” for UK citizens who want to continue their relationship with the EU, so they can continue to keep some rights, such as freedom to travel.
The UK voted by 52% to 48% to leave the EU in last year’s referendum.