Theresa May has insisted a proposed deal with the DUP to prop up her minority Government will not be allowed to undermine the Good Friday Agreement.
Following talks in Downing Street with Taoiseach Leo Varadkar, Mrs May said the terms of any arrangement between the Conservatives and the DUP would be made public once they were agreed.
"We continue our discussions with the DUP. We are talking about a confidence and supply agreement with them," she said.
"On reaching such an agreement we will make sure that the details of that are made public so that people can see exactly what that is based on.
"As a UK Government we remain absolutely steadfast in our commitment to the Belfast Agreement, its successor agreements."
Her comments follow warnings by Sinn Féin, the SDLP and the Alliance Party, that a deal with the DUP would undermine the British Government's attempts to restore the power-sharing executive at Stormont.
Mr Varadkar said he was reassured by the Prime Minister's commitment to make public the terms of any agreement.
"We spoke about the very important need for both governments to be impartial actors when it comes to Northern Ireland and that we are co-guarantors of the Good Friday Agreement and that any agreement that may exist between the Conservatives and the DUP should not in any way impact on the Good Friday Agreement," he said.
"I am very reassured by what the Prime Minister said to me today that that won't be the case."
The Conservatives have been in negotiations with the DUP since Mrs May lost her Commons majority in the General Election earlier this month.
A DUP source confirmed negotiations were "ongoing" and said they were looking to deliver "a more compassionate style of government for the whole of the UK".
The comments were seen as a coded reference to the party's opposition to scrapping the "triple lock" on pensions and means testing the winter fuel allowance - both of which were in the Conservative manifesto. It has also called for an end to the so-called "bedroom tax".
Mr Varadkar has marked his first visit to Downing Street, by comparing it to the classic Christmas film 'Love Actually'.
The Taoiseach said walking through the front door of Number 10 reminded him of the 2003 film starring Hugh Grant and Martine McCutcheon.
But he said at the start of the press conference afterwards that as soon as he walked into the building, he was reminded of one of the Christmas film's more famous scenes.
He said: "It's my first time in this building, so there is a little thrill in at as well.
"As we spoke on the way in, I was reminded of that famous scene in Love Actually where Hugh Grant does his dance down the stairs, but apparently it wasn't filmed here so I didn't get a chance to see the stairs."
"I was reminded of that famous scene in Love Actually where Hugh Grant does his dance down the stairs"- Irish PM's thrill of being at No. 10 pic.twitter.com/TLThYRiKht— Sky News (@SkyNews) June 19, 2017
He continued by thanking the British Prime Minister for his first overseas visit as Taoiseach at such short notice.
Mr Varadkar said: "It does emphasise the strength and closeness of the relationship between our two countries."