Officials from Dublin and Westminster will work together on efforts to avoid a hard border between the UK and Ireland after Brexit, Taoiseach Leo Varadkar said today.
Mr Varadkar said a comprehensive free trade and customs deal between the UK and European Union was the best way of avoiding problems at the border.
Following talks with Theresa May in Belfast, Mr Varadkar said both governments agreed that was the best approach and officials would "explore solutions" to the issue over the coming weeks and months.
Mrs May said the agreement reached on the first phase of the Brexit process in December still applied and "we are both committed to 'no hard border'".
The best way of achieving that was "in the context of the overall UK-EU economic partnership".
The EU's chief negotiator Michel Barnier has said that checks at the border will be "unavoidable" following the British Prime Minister's decision to leave the single market and customs union under her Brexit strategy.
The December deal on the first phase of the EU withdrawal talks signalled that the issue could be dealt with in one of three ways: through the overall Brexit deal as Mrs May wants, through some "specific solutions" proposed by the UK government or by maintaining "full alignment" with single market and customs union rules.
Mr Barnier confirmed that Brussels is drawing up a legal definition of the regulatory alignment that must continue between Northern Ireland and the EU.
London had provided no proposals for the kind of technological fix which could get around this, Mr Barnier said last week.
But Mr Varadkar and Mrs May said both the UK and Irish governments were working on "option A" - for the issue to be resolved as part of the overall Brexit deal.
He said: "What we agreed to do is co-operate at official level, the two governments exploring together how we can realise the commitments and guarantees that were given in December that a hard border between Northern Ireland and Ireland would be avoided.
"We have always said, and this is where the British and Irish governments are very much agreed, that the best way to achieve that is in the context of a new relationship between the UK and EU.
"So we are going to talk about that, but obviously any negotiations will have to be done through the Barnier task force and the EU27."
Mr Varadkar said the "tricky part" of the December agreement was going to be how to avoid the hard border.
"It's very much our view that needs to be stitched into the withdrawal agreement, the legal text of that agreement which is now being negotiated so that's very much on track," he said.
"It's also very much the view of both the British government and the Irish government, affirmed here today, that the best solution is not the backstop - as I call it - or the last resort - as Theresa May the Prime Minister calls it - but actually the option A, ensuring that we can have a new relationship between the UK and EU that involves a comprehensive free trade agreement and customs arrangement that allows us to avoid not just a hard border north and south but also new barriers to trade east and west."