Having accepted this position initially, David Davis, the Secretary of State for Leaving the European Union, has tried to get the trade relationship discussed in parallel.
The UK government has argued that there might be no customs implications at all for road and rail crossings if ambitious post-Brexit deal is struck.
The Irish Government has been more forthright about its concerns in recent weeks because both it and Brussels are trying to impress on London the need to come up with solutions that will avoid a hard Border.
However, under Union law, this is only possible if the United Kingdom stays in the customs union and in the single market/ the European Economic Area.
Mr Barnier's team also said Irish citizens living in the North must keep their rights as European Union citizens.
Sources at some of the UK's biggest businesses expressed incredulity at the request from No 10, which comes at a time when Theresa May's relationship with the private sector is already under strain.
Have another look of that Ben Woodburn's rocket vs Austria
So, when he saw young Ben Woodburn watching a Wales friendly against Holland in November 2015, he went for a quiet word. His perfectly angled header giving the keeper no chance. "It doesn't matter who scores the goals, it's a team game".
In them, the EU is expected to say the onus for solving the problems caused by the withdrawal in relation to the border - like leaving the single market and customs union - remains exclusively with the UK.
Michel Barnier's team said they were not offering solutions on how cross-Border trade and travel will be protected.
Army and police checkpoints along the border were lifted some 20 years ago after a peace deal involving Dublin that ended a long civil conflict in Northern Ireland between British loyalists and Irish republicans.
It called on the United Kingdom to make "substantive commitments and workable solutions".
The UK wants to avoid any physical border infrastructure in either the UK or Ireland, for any objective (including customs or agri-food checks). I also think of Canada, with whom we have negotiated a very ambitious free trade agreement, CETA.
However, Johnson told reporters that a suitable arrangement over the Irish border would be found between the negotiating parties and made light of the EU's concerns.
"The Union has consistently supported the goal of peace and reconciliation enshrined in the Good Friday Agreement in all its parts, and continuing to support and protect the achievements, benefits and commitments of the Peace Process will remain of paramount importance".