Direct rule from London is not an option amid the ongoing standoff between Sinn Fein and the DUP, the Taoiseach has insisted.
Dublin would expect to have "real and meaningful involvement" in Northern Ireland if efforts to restore Stormont powersharing fail, Leo Varadkar said.
Mr Varadkar's insistence that his government must have a say in Northern Ireland's internal affairs should the negotiations fail has infuriated unionists.
The British and Irish Governments are planning fresh efforts to reinstate the Assembly in Belfast - but Mr Varadkar has warned that time is running out.
It will be a year on January 16 since the late Martin McGuinness sparked an election in protest at Arlene Foster's role in the Renewable Heat Incentive scandal.
A series of deadlines set by London for the re-establishment of power-sharing have passed without significant progress, leading Mr Varadkar to say there are now "two options".
"The first option is another set of elections, which is an option, although it's hard to see what outcome would raise from that that would put us in a better position," the Fine Gael leader said.
"The second option is convening the British-Irish Governmental Conference, which would allow the two governments to implement the Good Friday Agreement in the absence of an Assembly and Executive in Northern Ireland.
"So essentially the Good Friday Agreement provides for matters that are not devolved to be dealt with by the British-Irish Governmental Conference, and that's what we will seek."
The bilateral body, a construct of the 1998 Belfast Agreement, brings together UK and Irish ministers to encourage co-operation on matters of mutual interest in Northern Ireland. It last met in 2007. The prospect of it being reconvened has whipped up a political row over the extent of influence the Republic might exert.
Unionists have been angered by the suggestion the conference could hand Dublin a substantive role in the internal affairs of Northern Ireland.
They insist the UK Government would be in sole charge of the region in the absence of a devolved Executive, and the conference would only offer a consultative role for the Republic.
DUP leader Mrs Foster has dismissed the conference as a "talking shop".
But Mr Varadkar categorically dismissed direct rule from Westminster. "We won't be supporting direct rule. We didn't support direct rule," he said.
Asked whether he was suggesting some form of 'joint rule', Mr Varadkar replied: "I wouldn't use the term joint rule, because that's not the term used in the Good Friday Agreement.
"The Good Friday Agreement speaks of a British Irish-Governmental Conference, which is not joint rule because obviously the legislative powers remain at Westminster - but it does involve real and meaningful involvement of the Irish Government."
But the Taoiseach said that would be a last resort after further efforts to get a deal between Sinn Fein and the DUP.
He said he was also "very conscious" that there are a number of other parties in Northern Ireland with a role to play.
"And I'm certain the Tanaiste and I will be meeting them over the course of January and doing anything we can do to get those institutions up and running again," he added.
Mr Varadkar said he and his deputy Simon Coveney hope to meet Stormont's political leaders next month as part of efforts to resolve the power-sharing crisis.
Speaking to reporters at an end of year briefing, Mr Varadkar also said he will be making efforts to improve relations with Theresa May's government in the new year.
"Relations obviously are a little bit strained, and they've been challenged by the events of recent months", he said, referencing the dispute over the potential for a hard border after Brexit.
"The reason that relations have become strained is because of Brexit.
"Brexit was not our policy.
"Brexit was a decision of the UK people, which we respect, and is being pursued by the Government in the UK. What has strained relations is that decision.
But we need to be grown up about it. And we need to get on with it and try to get the best outcome for the Irish people.
"I would speak with Prime Minister May probably every two weeks, and we do, I believe, have a shared and common objective, which is to get the best outcome for our people; for her the best outcome for the United Kingdom, for me the best outcome for Irish people, both here in this state and in Northern Ireland."