But Mr Johnson, who pulled out of a joint press conference with Mr Bettel because of noisy protesters, said there was still a good chance of a deal.

A government source said the gap the UK and Brussels needed to bridge to achieve a deal "remains quite large".

Mr Johnson was visiting Luxembourg to hold talks with the European Commission President Jean-Claude Juncker and the EU's chief Brexit negotiator, Michel Barnier, as well as Mr Bettel.

After the working lunch with Mr Juncker and Mr Barnier, Mr Johnson said he had been encouraged by the EU's willingness to engage with the UK in their shared desire to avoid a no-deal exit - but there had not been a "total breakthrough".

However, the European Commission said the PM had yet to present concrete proposals for it to consider and insisted any new plans had to be "compatible" with the existing withdrawal agreement, which has been rejected three times by MPs.

There was then confusion after Mr Bettel held a press conference without Mr Johnson amid noisy protests by anti-Brexit protesters.

Mr Bettel, who addressed the media on his own after the UK PM pulled out, said his counterpart "holds the future of all UK citizens in his hands" and suggested it was his responsibility to break the deadlock in the process.