European leaders will not allow the Brexit negotiations to move onto the next phase unless the Republic is happy with progress made on the future of the border, Leo Varadkar has said.
The Taoiseach has warned the UK his government will stall talks if a satisfactory deal on Northern Ireland is not reached.
His comments, while on an official visit to Canada, are likely to stoke tensions with Britain which wants the negotiators to start discussing the future relationship between the EU and UK.
Mr Varadkar rejected the idea that the Republic could become a pawn in the talks, saying it will have a major say in how Brexit develops.
"We will decide whether the UK has made sufficient progress when it comes to citizens' rights, the financial settlement and issues pertaining to Ireland, and only if we are satisfied that sufficient progress has been made on those three areas will we then give the go-ahead to talk about trade," he said.
"I think that puts us in a strong position so I doubt our European colleagues would come to the view that sufficient progress had been made if we didn't think so."
Mr Varadkar will today embark on a "fact-finding mission" along the US-Canadian border which some Brexit supporters have said is an example of how the EU/UK border on the island of Ireland could operate.
"I have heard them describe it as a soft border, I wonder if that is the case? There are people who have told me its not. There are passport checks and customs checks and when I flew in from the US I had to fill in a customs form.
"If we are going to have those debates and discussion in the months ahead, it's an advantage to have actually seen some of these borders in operation. It's very much a fact-finding mission," the Taoiseach said.
Mr Varadkar also hit out at Brexit supporters who have argued the EU is an impediment to trade, saying they are "wrong-headed".
"There's a view among people in the UK, particularly those who promote Brexit, that the EU is holding them back and making it harder for them to strike deals with Canada, Japan and the rest of the world. Actually that is not true, the EU is a facilitator of global trade," he said.
The Taoiseach was speaking as the UK released two more policy papers on goods and on confidentiality. Britain set out proposals to ensure that goods and services currently approved for sale across the UK and EU can continue to be traded after Brexit.
They urged the EU yesterday not to separate goods from their services in Brexit talks, further outlining its negotiating stance to try to nudge discussions forward to a second phase on future relations. Brexit Minister David Davis said the proposals were designed to smooth the way to "the freest and most frictionless trade possible".
The second paper set out the UK's position on future co-operation with civil courts in the EU, stating that families, businesses and individuals need "certainty" about how their cases will be dealt with following Britain's withdrawal from the EU. Britain is calling for a new reciprocal framework for civil law based on commitments to build on existing co-operation and to continue collaboration across borders.
Meanwhile in a further sign that negotiations will be protracted, Slovenian Prime Minister Miro Cerar said: "I think that the process will definitely take more time than we expected at the start of the negotiations.
"There are so many difficult topics on the table, difficult issues there, that one cannot expect all those issues will be solved according to the schedule made in the first place."
But Downing Street said it remained "confident" of making enough progress on the issues including Ireland for the European Council to give the green light to the second phase of Brexit negotiations when it meets in Brussels in October.