The President of the European Council, Donald Tusk, indicated that the EU would remain open to a change of heart in the UK.
Speaking to the European Parliament in Brussels on Tuesday morning, Tusk said the United Kingdom could have a "change of heart".
"There would be no sudden changes to the United Kingdom regulatory framework. we would give adequate notice and ensure that companies had sufficient time to implement any changed requirements", it said. "Our hearts are still open for you".
"We must maintain the unity of the EU27 in every scenario, and personally I have no doubt that we will", he said.
Tusk meanwhile stressed that the remaining 27 European Union states would push ahead with negotiations with Britain on its departure, urging London to say what it wanted in terms of post-Brexit ties.
Mr Verhofstadt also highlighted the British government's announcement that it would revert to a blue passport design after Brexit - with the Belgian MEP pointing out that such a passport change "was perfectly possible inside the EU".
Mr Tusk also attempted to raise the pressure on the British negotiating team by calling for more "clarity" about the Government's aim for the future relationship between the United Kingdom and the EU.
The demand is understood to have been led by Eastern European countries, including Poland, which boast some of the highest EU migration rates to the UK.
Guy Verhofstadt, the European Parliament's representative on Brexit issues, told MEPs on Tuesday morning that "We are coming to the most hard part of this negotiation".
During his speech in Strasbourg, Jean-Claude Juncker, the President of the European Commission reiterated Mr Tusk's message.
Multiple UK Government ministers, including Home Secretary Amber Rudd, have promised free movement will end the moment Britain leaves the EU.
In an exclusive interview with The Guardian newspaper, Johnson said up to 438 million pounds could actually be made every week in the United Kingdom once Brexit was finalised, a figure even higher than his original prediction that had been emblazoned on campaign buses and disproved by experts.
The UK government is under pressure to publish legal advice it has received on whether Article 50 of the Lisbon Treaty - the official mechanism for leaving the European Union - can be reversed.