A senior EU official has told RTÉ News that the border on the island of Ireland will remain "one of the very difficult issues" as the Brexit process moves into the second phase.
Speaking following the summit of EU leaders, which formally agreed that negotiations can get underway towards Britain's future trading relationship with the EU, the senior official said the Irish border issue exposed "the contradictions in the UK position."
"This is and will remain one of the very difficult issues, and we know that," the official said.
"Both because of the issue itself, on its own merits, but also because it exposes the contradictions in the UK position.
"That is that you can't at the same time have frictionless trade and be outside the customs union and the single market. The way to have frictionless trade is to be in those constructions.
"That's why they were created. And with the single market, (it was created) very much at the insistence of the Brits.
"Therefore this will continue to be a very difficult issue. I don't know whether it has become more or less difficult.
"The issue is inherently difficult, and as to what this language of Paragraph 49 (of last week's agreement between the EU and UK) means, it's one of the cases where the text means what it says." the official said.
Paragraph 49 of the EU-UK joint report on the border and other issues, reads: "The United Kingdom remains committed to protecting North-South cooperation and to its guarantee of avoiding a hard border. Any future arrangements must be compatible with these overarching requirements.
"The United Kingdom's intention is to achieve these objectives through the overall EU-UK relationship. Should this not be possible, the United Kingdom will propose specific solutions to address the unique circumstances of the island of Ireland.
"In the absence of agreed solutions, the United Kingdom will maintain full alignment with those rules of the Internal Market and the Customs Union which, now or in the future, support North-South cooperation, the all-island economy and the protection of the 1998 Agreement."
The British and Irish governments continue to be at odds over the meaning of Paragraph 49, how it squares with the Good Friday Agreement, and what "full alignment" means.
Speaking to reporters at the end of the summit, Taoiseach Leo Varadkar said: "I call it the backstop, Prime Minister May calls it a last resort. I don't mind what you call it, but I know what it is.
"It says that there won't be a hard border, no physical infrastructure, no checks and no controls, and that'll be achieved by maintaining full regulatory alignment," Mr Vadadkar.
