DAVOS, Switzerland (Reuters) - Britain’s impending departure from the European Union is not just about trade for Ireland but is an existential issue for its nearest neighbour, Irish Prime Minister Leo Varadkar told Reuters on Thursday.

The future of the border between EU-member Ireland and Northern Ireland, which will be the United Kingdom’s only land frontier with the bloc after its departure, is proving the major hurdle in the ratification of the Brexit divorce deal in London.

Police on both sides of the currently seamless stretch have warned that customs posts could be a target for the small number of militant groups still active in Northern Ireland after a 1998 peace deal ended three decades of violence in the province.

Speaking at the World Economic Forum in Davos, Varadkar highlighted those concerns to demonstrate his resolve in standing firm on the withdrawal agreement Britain agreed with EU leaders but is struggling to pass in its own parliament.

“Often when I talk about Brexit outside of Ireland, people talk about it as if it’s a trade deal, as if it’s about trade and jobs and the economy and migration”, Varadkar said in an interview .

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“All those things are important but this is different for Ireland, this is existential. We’ve had 20 years of peace in Ireland, increased North-South co-operation, and the foundation for all of that was the European Union. That’s why for us this is a very different question. This is at a different level for us.”

After the “backstop” insurance policy designed to keep the border open after Brexit was met with particular opposition in the British parliament, Varadkar said any alternative solution from London would have to achieve the same outcome - providing a legal guarantee and a workable mechanism to avoid a hard border.

With Ireland refusing to even countenance contingency plans for how the border would be managed in a no deal scenario, Varadkar said he believed all sides would cobble together a similar arrangement to the “backstop” given their need to abide by global trade rules and the terms of the 1998 peace deal.

“I think we’d be in a position where Ireland, the UK and the European Union would have to sit down again and come up with an agreement to avoid a hard border and the only way to do that is through alignment in customs and regulations,” he said

“So we’d probably end up after a difficult period of, I don’t like to say chaos, but certainly a difficult period of no deal with some sort of agreement that is very close to what has been rejected by the House of Commons.”