Michel Barnier is visiting the border between Northern Ireland, which is part of the United Kingdom, and the Republic of Ireland. Talks resume this week in Brussels; the European Union and Ireland have both called for progress on the border question by the end of June. This means that for the first time the European Union will have an external border on the island of Ireland, writes The Economist.What will be the political and economic consequences?During the sectarian "Troubles" of 1968-98, the Irish border was for much of the time heavily fortified.
Mr Varadkar acknowledged some unionists were anxious that Brexit could be used to undermine Northern Ireland's union with Britain.
"Backstop is needed in order to respect the integrity of the EU single market and the EU customs union", he said, adding that goods entering Northern Ireland must comply with the rules of the single market and the customs union code.
Customs checks between Northern Ireland and the rest of the United Kingdom would upset Northern Ireland's unionists, who are sensitive to anything that separates them.
"I don't think he does understand the wider unionist culture of Northern Ireland".
However, it is understood that such protocols have been relaxed in north-south relations over time, but that the government still considers that it is up to Dublin to inform Northern Ireland elected representatives if an Irish minister is visiting their constituency.
Superior refinery explosion: 11 hurt, miles evacuated
Fire Chief Steve Panger said local authorities were still working with federal agencies to determine the cause of the explosion. There were no reports of fatalities, and all of the refinery's workers have been accounted for, Husky Energy's Duvall said.
"We need to agree rapidly by June on several new points, on the scope of alignment, customs and regulations".
At the beginning of the all-island Brexit forum in Dundalk, County Louth, Mr Barnier said he knows that the so-called backstop has been the subject of "heated discussions in the UK".
"We are seeking practical, practical and operational, solutions to a complex problem". It is there because of the UK's red lines.
"This is why it is necessary to have a self-standing backstop solution". The backstop was seen as hugely controversial because it would keep Northern Ireland in the customs union and Single Market - something which Theresa May said would never be acceptable.
"The only future that we have on this island is to work together and that's what I want to do".
Both Mr Varadkar and Irish Foreign Minister Simon Coveney are still doing this, the DUP MP said, "and then today he waltzes into Northern Ireland as if he owned the place".