Major differences between Fianna Fáil and Sinn Féin, particularly over the EU, would make a coalition deal between the two parties impossible after the next general election, according to Taoiseach Bertie Ahern.
Mr Ahern has up to now refused to consider a coalition pact with Sinn Féin because political parties could not have "an army and an arsenal of weapons" and then get access to the State's security intelligence.
Following arms decommissioning, he said the issue was "now removed for SF", particularly if the Independent Monitoring Commission verified that the IRA has ceased operations.
However, IRA decommissioning would not be enough to make Sinn Féin a partner for Fianna Fáil, he told RTÉ's This Week.
"I like to serve a full mandate; I don't believe in these smart games of jumping out after two years or three years. I believe you are elected for a period, and you serve that period.
"How could I sincerely negotiate something with SF that would get me elected taoiseach and then think that I would run for five years because there are so many differences in our policies. I would hardly get through five days. The next European Council wouldn't work. So, you have to be honest, it wouldn't work."
He said he was "a pragmatic politician" interested in Ireland's success due to low taxes, high employment and a low national debt. "I am not interested in running a country that can't make up its mind on where we stand on Europe, or whether we are against that.
"Only a government that has stable parties in it can do that. Of course, it doesn't just apply to SF. You couldn't, in my view, have a government of Fine Gael, Labour and the Greens because they wouldn't agree on it either."
However, Fine Gael leader Enda Kenny insisted that Mr Ahern would keep Sinn Féin in mind as a possible coalition partner if Fianna Fáil and the Progressive Democrats could not make up the numbers.
"I don't exclude the possibility of Fianna Fáil doing business with Sinn Féin ... Given his [Mr Ahern's] track record for secret meetings and side deals done with Sinn Féin ... I frankly do not accept that Bertie Ahern would not do business with Sinn Féin," he told TV3's The Political Party.
Convinced the IRA has decommissioned its weapons, Mr Ahern acknowledged it could "take some time" before unionists were convinced.
All of the intelligence over the past few months, he said, has made it clear that the IRA has dismantled its intelligence and bomb-making operations. However, an end to IRA criminality would be more difficult to achieve since some members used it as "a flag of convenience" to cover their criminal activities.
"But the normal forces of the law can deal with that. What gave these people power in their area was not the fact that they were bully boys or criminals but that nobody could go near them because they were untouchables, because they had the backing of the Provisional IRA."
Following decommissioning, he said, these people would lose their local power base.
IRA violence would not return because this would damage Sinn Féin's political ambitions.
"Nobody knows that better than SF. SF has moved from being a 1 per cent party to now being a party that has a mandate to talk about.
"You don't have to be a political strategist to know that if what you achieved during 30 years was 1 per cent, and what you have achieved now is 10 per cent and rising in some areas - and done on the back of the peace process."
