David Davis, right, and Michel Bernier, left, begin Brexit negotiations in Brussels but Ireland's for Foreign Affairs and Brexit Simon Coveney has said failure to secure a withdrawal agreement will be disastrous for Ireland.
"I think it's fair to say that Northern Ireland is perhaps the most vulnerable part of Europe to a bad Brexit deal should that happen", he said. "Without that voice people in Northern Ireland will be disadvantaged in a major way and will be essentially relying on others to make the case for them".
Northern Ireland has been without a power-sharing executive since March and without a first and deputy first minister since January.
As he travelled to Belfast to participate in negotiations for the first time, Simon Coveney pledged to "spare no effort" in the process to salvage the crisis-hit institutions at Stormont.
The parties have until 29 June to reach agreement and have been warned that direct rule could follow if they can't.
"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.More news: Microsoft Might Be Making A Horizon Zero Dawn Like Game
Monday will see the first round-table meeting involving the governments and local parties in negotiations to restore devolution. Would we then say they shouldn't be in government in the Republic? "We are hopeful of getting a resolution to them as quickly as possible", he said.
Her failure to win a majority has put May under pressure over her Brexit plans from inside and outside her party and has prompted complaints about her choice of partner due to the DUP's stance on social issues such as gay marriage and abortion.
But speaking in Dublin after a meeting with the new Taoiseach Leo Varadkar, the DUP leader Arlene Foster said it was down to Sinn Fein whether an agreement is reached.
"Leo has a well-stated and clear position on it".
"We will oppose any deal which undermines the Good Friday agreement", Sinn Fein president, Gerry Adams, told reporters outside Downing Street, in reference to the 1998 peace deal that ended three decades of sectarian violence.
"Clearly the DUP are on the wrong side of the argument, cosying up alongside the Tory Government who are disrespecting the mandate of the people here, who asked to remain within the European Union", she added.