Minister for Foreign Affairs Charlie Flanagan has said he is personally saddened by the impending departure of the UK from the European Union.
The Brexit vote was "a bad decision" and this is "a sad day," he told RTÉ's News at One.
He said he agreed with President of the European Council Donald Tusk that "there are no winners" in this case.
Mr Flanagan added that he welcomed the certainty that there now was on Brexit, but admitted there were “long and complex negotiations ahead”.
The Brexit decision was regrettable, he said, but it was not of Ireland’s making.
“We need to ensure that Irish priorities are maintained by both the UK and the EU.”
He said he was encouraged by the inclusion of a paragraph in relation to Ireland in British prime minister Theresa May's letter triggering the exit of the UK from the European Union.
The Minister said that he was a great believer in the European process and that he continued to believe that Ireland’s membership has been beneficial.
“Yes there are imperfections. But one doesn’t close the door and turn out the lights, you have to continue engagement.”
Ireland’s position in relation to the border was very clear, he added. “An open invisible border needs to stay.”
Mr Flanagan called for common ground be dealt with first in negotiations, before the contentious issues.
“It is important that progress be made early on.”