The European Union's chief Brexit negotiator on Monday urged faster action on the fraught problem of the Irish border, saying there needs to be agreement by June on a way to keep it open.
The Northern Ireland-Ireland border will be the U.K.'s only land frontier with the EU after Brexit. Britain and the bloc agree there must be no customs posts or other infrastructure along the currently all-but-invisible 500-kilometer border.
But Britain also says it will leave the EU's tariff-free customs union. Officials from the two sides are trying to find a way to reconcile the two positions.
Britain rejects the EU's suggestion, which is to keep Northern Ireland inside the bloc's customs union. The EU says the U.K. has yet to propose a workable alternative.
On a visit to the border region, EU negotiator Michel Barnier said "we need to agree rapidly by June on the scope of all-island customs and regulations, the safety and controls that we need to respect the single market."
But the leader of Northern Ireland's largest pro-British Unionist party accused Barnier of listening only to the Irish side of the argument.
"We have tried to get him to understand the unionist position for the people of Northern Ireland, but he hasn't really responded to that and I'm disappointed about that," Democratic Unionist Party leader Arlene Foster told the BBC.
Barnier said in response: "My door is open."
Britain and the EU want to strike an overall Brexit agreement by October, so EU parliaments have time to ratify it before Britain leaves the bloc on March 29, 2019.