Britain and the EU will hopefully reach an agreement on sufficient progress in Brexit talks within “the next few days”, the EU’s chief negotiator has said.

Michel Barnier told an EU conference in Tallinn, Estonia that the “moment of truth” was approaching for Britain’s exit talks and that “real, sufficient progress” was in sight.

“I do hope in the next few days we will come up with an agreement on principles, and a real agreement,” he said.

“We need to have real, sufficient progress in the three key areas where the UK's decision has created a lot of uncertainty and fear even.”

Mr Barnier added: “The moment of truth is approaching, we have a council under the Estonian presidency on December 14 and 15, and I really hope that will be the point where we will see real, sufficient progress on the conditions of our separation.

“And that will allow me to recommend the opening up of the next two phases of negotiations, first of all on the transition period and then on the future relationship.”

The EU official's reference to "the next two phases" raises the possibility that transitional arrangements might be discussed before a full trade negotiation is put on the table by the EU.

The chief negotiator’s upbeat comments however come as the Irish foreign minister Simon Coveney said on Monday that the UK needed to give more assurances over the status of the Irish border for sufficient progress to be made.

Other than the Irish border, European Council president Donald Tusk has said “much more progress” is also needed on the issue of the financial settlement – the question of what the UK will pay when it leaves the bloc.

Theresa May and David Davis has been given a 4 December deadline to make the progress on the two issues ahead of the make-or-break summit in Brussels.

The EU, Ireland, and UK are wrestling with how to avoid a hard border between the Republic of Ireland and Northern Ireland – as required by the Good Friday agreement – while also ensuring the EU still has an external customs border.

The European Parliament and European Commission have suggested customs checks could be moved to ports on the Irish Sea, effectively keeping NI in the customs union and putting a customs between two parts of the United Kingdom.

The DUP, on which the Government relies on to have a majority in the House of Commons, has however ruled out any such plan, as has David Davis the Brexit Secretary.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

On the financial settlement, the EU is demanding more detail than Theresa May gave during her Florence Speech, where she said only that "the UK will honour commitments it has made during the period of our membership".