A spokesperson for the Taoiseach says Britain's commitment to a Brexit border 'backstop' is legally firm and will apply until something better is agreed.
Yesterday's 'transition' deal allows talks on the UK's future trade relationship with the EU to be triggered later this week.
Some issues remain undecided - including the border - but Tánaiste Simon Coveney says that doesn't mean it's been kicked into the long grass.
He said a “legally operational” version of the backstop arrangement will now be negotiated “sooner rather than later.”
“Effectively that says that in the absence of agreement the UK will maintain full alignment with the rules of the customs unions and single market to protect North South cooperation, an all-island economy and the Good Friday Agreement,” he said.
“That is pretty clear to me what that that means.”
He said the British negotiators had now committed to entering into negotiations on the legal basis for the backstop.
Chief British negotiator David Davis said the UK has agreed to include a legal text outlining a backstop solution that is “acceptable to both sides.”
“It remains our intention to achieve a partnership that is so close as to not require specific measures in relation to Northern Ireland," he said.
The British Prime Minister Theresa May had previously warned that no UK Prime Minister could agree to the backstop arrangement in its current form.
European leaders will decide on Friday whether to allow the talks to move forward onto the future relations between the two blocks.
Yesterday evening, Labour Party leader Brendan Howlin warned that the Brexit Treaty deal is a 'worrying step backwards.'
He warned that the agreement had been ruled out before and despite the fact it “has now been ruled back in again,” we are no closer to finding a technical way to put it in place.