The only way to avoid a hard border in Ireland after Brexit would be for Northern Ireland to continue to apply the rules of the EU single market and customs union, Taoiseach Leo Varadkar has said.
But he said this did not necessarily mean the UK or Northern Ireland remaining members of either area, suggesting that a "bespoke" arrangement may be reached as part of the Brexit negotiations.
And Northern Ireland Secretary James Brokenshire indicated that the British government was ready to be "pragmatic" in seeking a solution to the "unique circumstances" created in Northern Ireland, which will have the UK's only land border with the EU after Brexit.
The Taioseach's comment came in response to the leak of a European Commission document which suggests that the Republic is now pushing hard for concrete reassurance on the border question ahead of the crucial EU leaders' summit in December at which British Prime Minister Theresa May hopes to gain a green light for trade talks to begin.
The one-page paper entitled "Dialogue on Ireland/Northern Ireland", which was obtained by the Daily Telegraph, states that in order to preserve the Good Friday Agreement peace deal, the Brexit divorce deal must respect "the integrity of the internal market and the customs union".
Along with the question of expat citizens' rights and the UK's "divorce bill", the Irish border is a key issue in the first stage of Brexit talks, on which "sufficient progress" must be made before the leaders of the remaining 27 EU states will give the go-ahead for trade talks. Any obstacle to finding a solution in time for the December summit would be a considerable blow to Mrs May's hopes of moving on to phase two of negotiations by the end of the year.
Speaking at the British-Irish Council summit in Jersey, Mr Varadkar said he was "loth to comment in too much detail on papers that have been leaked to the media".
But he added: "When it comes to the border between Ireland and Northern Ireland, what we have all agreed to is that there shouldn't be a hard border, there should be no physical infrastructure along that border and that there should be no return to the borders of the past.
"It is our view, and has been our view for a very long time, that the only way that can be achieved is if the United Kingdom as a whole or Northern Ireland continues to apply the rules of the customs union and the single market. That doesn't mean that they have to be members of it, but it would mean continuing to apply the rules of the single market and the customs union.
"That's the position that we hold and the best way to achieve our common objectives."
Mr Brokenshire stressed that Mrs May had made clear that the UK will be leaving both the single market and the customs union under Brexit, which is due to have effect in 2019.
But he added: "We are very clear on the need to be pragmatic and open to these practical solutions that recognise the unique circumstances. That is what David Davis, the Secretary of State for Leaving the EU has been focused on in his negotiations in this first phase - making that sufficient progress - and I think there has been good progress."
Mr Varadkar noted that the Isle of Man was not a member of either the UK or the EU, and traded with each under a protocol to the Treaty of Rome which involves the island applying the body of EU law, known as the "acquis".
"We are looking for a bespoke solution here that achieves the objective that we all share, which is no hard border, no return to the borders of the past and no physical infrastructure along that border," he said.
Speaking alongside Mr Varadkar at a press conference at the end of the summit, Mr Brokenshire added: "Absolutely we do want to see a positive outcome for Northern Ireland through the Brexit talks, as for all parts of the United Kingdom.
"We do acknowledge that there are unique circumstances that will require practical, pragmatic solutions, bespoke solutions, that we as a Government are determined to advance and see secured.
"This isn't some sort of abstract context. It's actually about how people live their lives on the island of Ireland, the ability to work, to study, to see family, to see relatives, just being able to seamlessly go across the border from Northern Ireland to the Republic of Ireland. Absolutely, that is what we want to see preserved into the future."
Mr Varadkar added: "There is no demand from the Irish Government that any part of the United Kingdom should remain in the customs union or the single market.
"The United Kingdom would be welcome to if it wishes to, but it's not our demand that the United Kingdom should do so.
"What we want, though, is the language that we've all agreed to to be turned into reality. We've agreed that there will be no hard border in Ireland, that there will be no physical infrastructure and that there will be no return to the borders of the past. How do we actually realise that and make that a practical fact, so that people can continue to live their lives as normal on the island or Ireland?
"We believe that can be best achieved by continuing to apply the same sort of rules and regulations. If we do that we can avoid those things we wish to avoid."
