This undated photo shows freight traffic arriving from Scotland at Larne port in Co Antrim, Northern Ireland. (PHOTO / BLOOMBERG)

The UK and European Union (EU) are on course for a fresh confrontation over Northern Ireland, with the bloc warning of “swift” and “firm” action if Britain again breaches the terms of the Brexit deal.

Ahead of a key meeting with Britain’s Brexit minister David Frost on Wednesday, European Commission Vice-President Maros Sefcovic warned Brussels would react strongly if the UK fails to implement the parts of the Brexit deal relating to Northern Ireland.

If the U.K. takes further unilateral action over the coming weeks, the EU will not be shy in reacting swiftly, firmly and resolutely. Unfortunately, we see numerous and fundamental gaps in the UK’s implementation.

Maros Sefcovic, Vice-president of the European Commission

“If the U.K. takes further unilateral action over the coming weeks, the EU will not be shy in reacting swiftly, firmly and resolutely,” he wrote in an article for the Daily Telegraph. “Unfortunately, we see numerous and fundamental gaps in the UK’s implementation.”

The accord - which UK Prime Minister Boris Johnson agreed to less than two years ago - created a trade border in the Irish sea, roiling supermarket supply chains and stirring violent protests among Northern Ireland’s unionists. Tensions between the UK and EU have been rising for months, with the British criticizing the bloc’s “legal purism” and calling for more flexibility.

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But in a move that threatens to further undermine trust between the two sides, the UK is considering a unilateral extension to a grace period that allows sausages and other chilled meat products to continue to be moved from Great Britain to Northern Ireland, the Telegraph reported, without saying how it got the information. The grace period is due to expire on June 30.

The EU’s patience is running thin and it could use all the tools at its disposal if the UK fails to put a stop to unilateral actions and threats, according to an official who asked not to be identified discussing confidential matters. They said that earlier infringement and arbitration procedures weren’t working.

Under the terms of the Brexit deal, both sides have the right to impose retaliatory tariffs in extreme circumstances. Separately, the EU could prevent the UK financial services industry getting access to the single market.

The dispute is escalating at a sensitive time for Johnson, who hosts world leaders in the UK for the Group of Seven summit later this week. Brexit encroached on a phone call Johnson held with French President Emmanuel Macron on Monday, ahead of the gathering.

Johnson told Macron that “both the UK and the EU have a responsibility to find solutions” to the dispute over Northern Ireland, according to a spokesman for the British premier’s office.

The onus is on the UK to fulfill its obligations or face a much more confrontational future, said the EU official, who said Brussels experts still did not have access to the most basic IT systems to determine what goods are moving where, and thus assess risks linked to plant and animal health.

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The EU is open to finding solutions, but there are limits to what can be achieved given the political decisions the UK has made, the official said. Solutions can only be found within the framework of the protocol, the official added.

Defending the UK’s stance, Environment Secretary George Eustice said the EU needed to show flexibility to resolve the impasse.

“The protocol always envisaged that both parties would show best endeavors to make the protocol work,” Eustice said on Sky News on Tuesday. “What we really need the EU to do is respect that.”