TALLINN (Reuters) – Ireland dismissed British proposals for the Irish border after Brexit as unconvincing on Friday, a day after the EU chief negotiator said they amounted to a demand the bloc suspend its laws for Britain.

But British Foreign Secretary Boris Johnson, speaking at a meeting of EU foreign ministers in Tallinn, said a solution was “not beyond the wit of man”.

The border between the Irish Republic and the British province of Northern Ireland is currently open to free flow of goods, being an internal EU frontier. But when Britain leaves the bloc, it will become subject to EU customs regulation.

Establishment of a physical border could revive security concerns, 20 years after a peace deal involving Dublin that ended a long civil conflict in Northern Ireland and led to the end of army and police checkpoints.

Britain has proposed an “invisible border” without border posts or immigration checks between the two after Brexit, but given no firm proposals how the customs frontier between Northern Ireland and the Republic would be monitored.

EU Brexit negotiator Michel Barnier said on Thursday British proposals would undermine the bloc’s single market. He said Britain in effect wanted the EU to “suspend the application of its laws” as a test case for broader EU-British customs regulations. “This will not happen.”

Ireland’s Foreign Minister Simon Coveney told Reuters on Friday: “The maintenance of an invisible border on the island of Ireland would be a lot easier if Britain were to remain in the customs union.”

That is something Prime Minister Theresa May has said would not happen, though her cabinet is split on the issue and some have floated the idea of a transition period after Brexit that would still leave Britain in the EU customs union.

BRITAIN‘S OBLIGATION

“Britain is the one leaving, they have an obligation to try and design unique solutions…. We cannot have a physical border on the island of Ireland again that creates barriers between communities,” Coveney said.

“We cannot and will not support that and nor will the European Union,” he said, adding that Britons wanted to avoid a hard border too. “The problem is that the solutions to actually get us there so far haven’t been convincing.”

Negotiations to extricate Britain from the EU have seen a slow start and Brussels has repeatedly warned that time is running out to answer complex questions before Britain is due to leave in March, 2019.

The bloc, which will have 27 member states after Brexit, wants to solve key exit issues before opening talks about any future trade cooperation with Britain. London says divorce talks should run in parallel with discussions about future ties.

But, with slow progress on agreeing Britain’s divorce bill, ensuring expatriates’ rights and deciding on the Irish border, the EU now doubts it will give a green light in October for starting talks about the post-Brexit order, as had been planned.

The EU worries London may try to use the Irish border as a template for a broader trade pact with the EU after Brexit. It believes Britain’s proposals risk affecting the bloc’s single market and customs union.

The European Parliament’s chief Brexit speaker, Guy Verhofstadt, dismissed Britain’s plans for an “invisible border” as surreal.

“We are nowhere on border issues,” one senior EU official said.

But, asked if he was confident that Britain would get a deal with the EU, Johnson said in Tallinn: “Absolutely, with rock solid confidence.”

He reiterated London’s stance that the divorce talks should run together with discussion about the post-Brexit relationship.

“Article 50 makes it very clear that the discussion about the exit of a country must be taken in context with discussion of the future arrangements. And that’s what we’re going to do,” he said.