Taoiseach Leo Varadkar says he believes the majority of people in Northern Ireland will be Irish citizens after Brexit.
He was speaking in Brussels following a series of meetings with other EU leaders.
He says sufficient progress has not yet been made in the Brexit talks, but is hopefully progress will be met by December.
"But we're not there yet, and we aren't able to agree to sufficient progress today."
Mr Varadkar discussed the situation with the Nordic and Baltic states.
"One point I made to them, which is one I think that does surprise some European leaders, is that after Brexit... it's very likely that the majority of people in Northern Ireland will be Irish and European citizens.
"Even people from a unionist background will want to become Irish and European citizens, at the very least for the convenience."
Taoiseach Leo Varadkar speaks to the media in Brussels | Image: © European Union
"So I think more and more European leaders are understanding the unique situation that pertains to Northern Ireland: a territory that's going to be outside the European Union in which the majority of citizens are European citizens - and the majority of which at least voted to stay in the European Union".
He also denied the Brexit talks are near a "cliff-edge" - and that there was plenty of time left.
"I think we've a way to go yet - Brexit doesn't happen until April 2019, so we're quite far back from the cliff-edge at this stage.
"But it's incumbent on all European prime ministers and presidents to ensure that we don't sleepwalk towards that cliff, and that substantial more progress is made in the next couple of months.
"But we're well away from the cliff".
Pushed on progress in the talks, Mr Varadkar says: "I think it is possible to get to the point where we can achieve sufficient progress by December.
"That's not just about Ireland, it's also about the rights of citizens - which are really important - it's also about the finances, which quite frankly I think are less important, what's more important is what happens to citizens to me.
"So I think we can get there. I think we will require some further concessions from the UK government, which will be met with greater understanding I think from the European side".