The EU's chief Brexit negotiator Michel Barnier said Friday the thorny issue of the border between Ireland and the British province of Northern Ireland could sink the negotiations on Britain's exit from the European Union.
"The answer is yes," he said when asked on France Inter radio if the Irish border issue could cause the negotiations to collapse. "I believe we need a deal. I'm not yet sure we'll get one. It is difficult, but possible."
European Union leaders warned Britain on Thursday they would offer no more concessions to break the deadlock in Brexit negotiations, but expressed confidence that a deal can be done before the country leaves the bloc next March.
A Brussels summit wrapped up without progress after British Prime Minister Theresa May offered no new proposals, beyond suggesting she could accept a longer transition period after Brexit.
May has been struggling since the 2016 referendum vote to leave the EU to reconcile the demands of her eurosceptic Conservative party with the realities of negotiating with Brussels.
Her difficulties were laid bare by the fury sparked back home at her suggestion that she could extend a post-Brexit transition period to address the Irish border issue.
Both sides have agreed there should be a legally-binding "backstop" arrangement to avoid frontier checks between British Northern Ireland and EU member Ireland if and until a new trade deal solves the issue.
This would come into effect after the transition ends -- but both sides strongly disagree on its terms, and the issue is holding up the rest of the Brexit talks.
Britain crashing out of the EU without an agreement is viewed as potentially catastrophic as tariffs, customs and regulatory issues could severely disrupt trade.