Sinn Féin have told Britain's prime minister that she must deliver on promises she made to protect the Good Friday Agreement.
Speaking after a phone call with Theresa May on Thursday, the party's leader Mary Lou McDonald said she made it clear that any decisions taken on the UK's departure from the EU must protect citizen rights and avoid a hard border.
"We had a phone call with Mrs May around lunchtime, it was quite a detailed conversation, where we set out for her the consequences of a crash Brexit," Ms McDonald said.
"She informs us that efforts are underway to secure some level of agreement in Westminster and she states that it is not her intention or preference to exit without a deal.
"However, the reality is, that as we speak, that is still a very live possibility.
"We've put it to the prime minister that at the beginning of this Brexit debacle commitments were given to protect the Good Friday Agreement in all its parts, to prevent any hardening of the border and to ensure the protection of citizens' rights.
"She didn't give us any assurances as to how this would be achieved in the absence of any agreement.
"I think it's important we understand that Irish prosperity, in addition to being linked to single market is also linked to the all-island economy.
"It's not just about the economy and trade, its not a technical dilemma, it's a political question and the idea of reinstating the border on the island of Ireland is almost like suggesting we rebuild the Berlin wall.
"We have to be very, very clear that we must protect political progress and we set all of that out for Mrs May this morning.
Ms McDonald says she believes that the prime minister is dedicated to leaving the EU with a deal, however, she is unsure how Mrs May will proceed as Westminster remains deadlocked.
"I have the clear sense that reaching a deal is her first preference, and that is the course of action she has set out," Ms McDonald said.
"I can't guess where this will land and I suspect she might be in the same position – which is cause for concern for all of us.
"There's no use saying you support the Good Friday Agreement, we need actions.
"We told her in no uncertain terms that the commitments given in the beginning must be honoured."
The call comes as efforts intensify to find a way through the Brexit impasse.
The UK government and the Labour Party's negotiating teams are locked in intensive talks in the hope of agreeing a position which could win a majority in the House of Commons in the coming days, allowing Theresa May to request a short delay to Article 50.
