LONDON (Reuters) - The leader of the Northern Irish political party that props up British Prime Minister Theresa May’s government said the European Union’s chief negotiator needs to do more to understand the views of unionists, the BBC reported on Monday.

Slideshow ( 2 images )

Northern Ireland will be the UK’s only land frontier with the EU after its leaves the bloc in March 2019. Both sides say they are committed to keeping the border with Ireland open, but finding a practical solution has proved elusive so far.

Arlene Foster, leader of the Democratic Unionist Party, said EU chief Brexit negotiator Michel Barnier needed to understand that any solution that divides Northern Ireland from the rest of the United Kingdom will not get her party’s support.

“Michel Barnier’s trying to present himself as someone who cares deeply about Northern Ireland, and if that is the case he needs to hear the fact that we are part of the United Kingdom (and) will remain part of the United Kingdom constitutionally, politically and economically,” Foster told the BBC.

“I don’t think he does understand the wider unionist culture of Northern Ireland,” Foster said. “His proposal of us being in an all-Ireland regulatory scenario with a border down the Irish Sea simply does not work.”

Britain says an EU-UK free trade deal to be sealed by 2021 can resolve the border issue. Dublin insists the Brexit treaty must lock in a “backstop” arrangement in case that future pact does not work, something London signed up to achieving last month.

Barnier, speaking in the Irish city of Dundalk ahead of a visit to Northern Ireland, said Foster failed to understand that he was representing the interests of the 27 countries who will remain in the EU after Brexit and not those of the United Kingdom.

“I am the negotiator for the 27. Mrs Foster and some others need to understand that and respect that,” Barnier told a press conference with Irish Prime Minister Leo Varadkar.

“I am not willing to engage in any kind of polemics with Mrs Foster,” he said.

Barnier said Britain and EU negotiators must make rapid progress on the border issue by a June EU leaders meeting that will be a “stepping stone” towards attempting to reach a final Brexit deal in October.