Stormont parties supporting a united Ireland do not have a majority, the taoiseach has said.
Leo Varadkar said despite the election of more nationalist than unionist MPs in this month's Westminster poll, there was not enough support for a border poll.
The result was unprecedented amid Brexit-fuelled calls in some quarters for a referendum on Irish unity.
Sinn Féin's John Finucane triumphed over the DUP's Nigel Dodds in North Belfast in one of the republican party's stand-out successes.
Mr Varadkar said parties that supported a united Ireland did not have a majority, at around 40%, adding that was why he was opposed to holding a poll on Irish unity now.
He added: "That is still well short of the 50% plus one that you would need to win a border poll.
"That is why I don't think that a border poll is a good idea. I don't see that we would gain from that sort of scenario."
He said recent elections had shown a change in political sentiment amongst the electorate.
"If you look at the results of the recent Westminster elections in Ireland and you take them with European elections, local elections, the assembly elections, then you do see that there has been a change," he said.
"For the first time since the foundation of Northern Ireland, unionist parties do not have a majority.
"They definitely don't, it was not a one-off, it is four elections now of different sorts."
He said political leaders needed to rededicate themselves to the 1998 Good Friday Agreement, powersharing in Northern Ireland and North/South cooperation.
He noted the significance of the surge in representation of non-sectarian parties such as the cross-community Alliance Party in the recent election.
Negotiators in Belfast are bidding to restore devolution by next month.
The taoiseach said: "When we have the institutions up and running properly then there is time to have a long look at the institutional arrangements and the constitutional arrangements.
"We have to learn from our history and we have to understand that there are a million people on this island who are British and are unionists so we need to respect that and make sure that they are part of the future and they feel part of the future."
The taoiseach has previously ruled out sponsoring a forum on Irish unity in anticipation of a poll on abolishing the border, arguing that such a move would be divisive and provocative to unionism.
The implications of Brexit, with Northern Ireland being taken out of the EU against the will of a majority of its people, has sparked fresh calls for a border poll from Sinn Féin and others.
