Taoiseach Leo Varadkar has warned that the peace process in the North must be protected whatever the outcome of the Brexit negotiations.
Mr Varadkar said he wants to ensure there is no return to a hard border that would restrict trade and movement of people .
He was speaking at the Londonderry Chamber of Commerce, where he said he would do all he could to make the case for Northern Ireland during negotiations.
Speaking at the Chamber's annual President's dinner, Mr Varadkar said: "Perhaps no part of Europe will be affected by Brexit more than areas such as this one," he said.
"Our priorities are clear. We must protect the peace process and ensure there are no new barriers to trade or movement of people across our island.
"We are committed to safeguarding the Common Travel Area and the associated rights enjoyed by Irish and UK citizens - a commitment that is shared by the UK Government and supported by the EU.
"We also hope that the ultimate outcome of the negotiations will be the closest possible trade and customs relationship between the UK and the EU."
Speaking earlier as the Cabinet met in Cork, Mr Varadkar said he fears preparations for a hard Border after Brexit could become "a self-fulfilling prophecy".
Mr Varadkar said the Government was committing every diplomatic resource possible to avoid the re-introduction of Border customs controls.
Earlier this week, an unpublished Revenue Commissioners report laid bare the possible impact of Brexit on everything from ports to the postal service.
It starkly warned that an open Border would be impossible from a customs perspective.
British Chancellor Philip Hammond later said cameras and other infrastructure along the Border would be deemed a "legitimate target" and risk undoing the peace process.
Yesterday, the Taoiseach said a hard Brexit would be a "political failure all around".
"Of course we have to prepare for all scenarios but preparing for all scenarios and doing desktop planning and war-gaming is a far cry from what some people seem to be suggesting.
"Some people seem to be suggesting we should admit defeat already. That we should start implementing the worst-case scenario - looking for sites for truck stops and customs posts and training dogs.
"I can absolutely guarantee you that is not the kind of preparation we are doing.
"When you start doing that kind of preparation, there is a risk that it becomes a sort of self-fulfilling prophecy."
Mr Varadkar's comments came as relations between Europe and Britain remained strained. UK Chancellor Phillip Hammond was forced to apologise for describing the EU as "the enemy".