The Irish government expects a possible future border poll on the reunification of Ireland to feature in Brexit negotiations.
Ireland's most senior diplomat in the UK suggested to Sky News that Brexit could impact on some elements of the Good Friday Agreement, which presumes the EU membership of both the UK and Ireland, and so the border poll issue should be "specified" or "clarified" in talks.
Ambassador Dan Mulhall said: "It may need to be made clear in the context of the Brexit agreement, or the agreement on future negotiations, that if that were to happen Britain leaving the EU would not change that situation; would not alter that commitment that the British Government made in the Good Friday agreement to respect the outcome of that border poll when it takes place in the future."
Last month, Irish Prime Minister Enda Kenny said: "I will defend the Good Friday Agreement, in its spirit as well as its letter."
Speaking to Sky News, Mr Mulhall said: "It was a reflection of the fact that concern has been raised in some quarters that this matter needs to be specified, needs to be clarified for the avoidance of doubt."
He also confirmed that the Irish government had begun technical work on new customs arrangements on the Ireland-UK border as a contingency.
"Of course it would be a dereliction of duty for any government facing negotiations where the outcomes are inevitably uncertain - because in any negotiation there are any number of outcomes - so there have to be technical explorations of contingencies," Mr Mulhall said.
But he added: "The clear political message from our government is that we will not accept a hardening of the border because we believe it would be damaging for Ireland's interests, for the interest of north-south relations in Ireland, for Irish-UK relations and indeed for the European Union because it would put at risk something that has been a great achievement of the European Union - which is the lifting of the burden of that age-old conflict."
The ambassador spoke to Sky News ahead of the result of the Northern Ireland Assembly election that saw support for Sinn Fein surge, leaving it with just one less seat than the Democratic Unionist Party.
Unionism lost its majority in the Assembly for the first time in its nearly 19-year history.
Northern Ireland Secretary of State James Brokenshire has been in Stormont today attempting to broker an agreement for the re-establishment of a devolved government with party representatives.