Taoiseach Leo Varadkar has warned British prime minister Boris Johnson that London will still face "years" of talks with the EU even if it forces a no-deal Brexit - saying the stand-off "doesn't end" on October 31.
Mr Varadkar said he is not "fatalistic" about a no-deal Brexit being unavoidable and downplayed the possibility of a border poll as a result of the crisis.
At the iconic Hillsborough Castle on the outskirts of Belfast, where the Anglo Irish agreement was signed in 1985, Mr Varadkar said despite growing tensions he still believes a no-deal Brexit can be avoided.
However, even if the worst-case scenario outcome happens, the Taoiseach said London will still face "years" of talks with the EU that would undermine any British desire to be free of the long-running negotiations.
"Well you know I can't speak for the UK government, but there is one thing that I would like to say and perhaps it isn't fully appreciated. This doesn't end on October 31.
"You know some people, I know, have become weary of Brexit and they may take the view that this should end on October 31- either with a deal or with no deal. This doesn't end on October 31.
"If there is a deal, we are going to enter into several years of negotiations on a new free trade agreement with the UK and a new economic and security partnership.
If there is no deal, then at a certain point we will have to begin negotiations again and the first items on the agenda will be citizens rights, the financial settlement and the solution to the Irish border.
"So Brexit isn't a storm that we weather or a severe weather event that we prepare for. It is a permanent change in relations between the European Union, including Ireland, and the United Kingdom. And I think that needs to borne in mind.
"What I am saying is that it doesn't end on October 31, if we have no deal, we are going to have to talk, and the first things on the agenda are going to be citizens rights, financial settlement and the solution to the Irish border- before we even start to talk about a free trade agreement.
"If there is a deal, well then we can start to talk about a free trade agreement and a new economic and security partnership so this goes on and on and on for many, many years.
"This doesn't end, this is a permanent new status and a permanent change in the relationship between the EU and Ireland on the one hand and the UK on the other," he said.
Mr Varadkar, who was invited to Hillsborough Castle by local DUP MP Jeffrey Donaldson, will later meet with business representatives from both sides of the border and a cross-community arts group.
He will this evening take part in a Feile an Phobail "leaders debate" on the Falls Road alongside Sinn Féin leader Mary Lou McDonald, at which point he is likely to be questioned on the likelihood of a border poll due to Brexit.
Asked about the issue this morning, Mr Varadkar said: "What I said [in the Glenties last month] was that it was very much my view that I wouldn't like to see Brexit bring constitutional questions to the fore. But we can't bury our heads in the sand. If we ended up in a no-deal scenario that could well happen.
"On the question of the border poll, my position and that of Government has always been that we don't favour a border poll at this time, we believe there would be a high probability that it would be defeated and that it would be divisive I think here in Northern Ireland.
"However, the Good Friday agreement, and I always come back to the Good Friday agreement on these matters, the Good Friday agreement points out that the aspiration to Irish unity is one that should be respected and one that should have parity of esteem in the same way the aspiration to sustain and retain the union should be respected.
The Good Friday agreement does include provision for a border poll at a certain point in time, under certain circumstances, and that is what the principle of consent is all about, that Northern Ireland is part of the United Kingdom because the people of Northern Ireland want it to be.
"But the people of Northern Ireland have a choice to change that by referendum in the future, but it's not something that I am looking for."
The Taoiseach was asked if it "frustrates" him that the backstop is repeatedly framed as an Irish issue, despite it being created due to British government red lines.
"Not at all, but I'm surprised it [that claim] isn't going challenged a bit more."