The former taoiseach said a border poll could take place on the 30th anniversary of the Good Friday Agreement.
Bertie Ahern has told Newstalk that a vote on re-uniting the island of Ireland should be held in 2028 after the Sunday Times found a majority of respondents polled in Northern Ireland would like it to take place within five years.
Claiming that a referendum on uniting Ireland is not “for now”, Ahern said he told former US senator George Mitchell, Tony Blair and Bill Clinton that he would support such a vote being held on the 30th anniversary of the Good Friday Agreement, provided certain conditions were met.
“I said at that stage two things have to happen,” Mr Ahern explained.
“One is that we have to have institutions under the Good Friday Agreement that were stable for a prolonged period – we haven’t had that ever since the agreement in 23 years.”
“I don’t like the idea of ‘border poll’, because it is an issue of sovereignty and how it will happen.
“The second point I made was the propriety work that made sense of all of this, which has really only commenced. There’s the Shared Island unit, which is something I support.
“There’s a whole lot of other academic work going on.
“Both of those things have to happen and what I said at that stage, that any idea of a vote that was seen in the Good Friday Agreement, should be probably on the 30th anniversary of the Good Friday Agreement, which is at the end of the decade.
“I don’t see it being held in the short-term and I think those two conditions have to be fulfilled.
“On the other side, it was an absolute understanding to bring republicans and nationalists on side, that somewhere in the future would be a poll. That was set out in the constitutional section of the Good Friday Agreement and also in the British-Irish Agreement which is the annex to the GFA.
“That aspiration has to be there and it has to be fulfilled. I don’t think it’s for now.”
Mr Ahern’s comments come after a majority of people in Northern Ireland polled by the Sunday Times said they would like an Irish Unity referendum in the next five years.
The poll found 47% of people in Northern Ireland want to remain in the UK, with 42% favouring a united Ireland, and 11% remaining undecided. Only 44% are against holding a vote within five years.
It also found voters across the UK believe Scotland will become independent within ten years.
First Minister Arlene Foster said holding a border poll on a united Ireland would be “absolutely reckless”, whilst Ahern said politicians would have to be mindful of the “anxieties” of loyalists about the new border in the Irish sea and on the island of Ireland.