The U.K. inflamed tensions with the European Union by reneging on part of their post-Brexit settlement, saying it would unilaterally change trade rules relating to Northern Ireland.

The British government said it will waive customs paperwork on food entering Northern Ireland until October, beyond the April 1 deadline it had agreed on with the EU. The U.K. had asked for the deadline to be extended, but the bloc hadn’t given its consent.

Northern Ireland Secretary Brandon Lewis said Wednesday in a written ministerial statement that the government “is taking several temporary operational steps to avoid disruptive cliff edges as engagement with the EU continues.”

“These recognize that appropriate time must be provided for businesses to implement new requirements,” he said.

Trade across the Irish Sea has been one of the most contentious features of Britain’s post-Brexit relationship with the EU, as companies have had to grapple with new paperwork and frictions on commerce. An EU official said Britain’s move wasn’t an extension of a grace period because it wasn’t mutually agreed on, and that U.K. action is in breach of the Brexit deal.

Ireland’s foreign minister Simon Coveney said the U.K.’s decision was “deeply unhelpful” to fostering trust between Britain and the EU.

“It is vital that the current challenges are addressed in a spirit of cooperation and partnership,” Coveney said, following a meeting on Wednesday with Lewis and David Frost, who negotiated the Brexit trade deal with the EU and was recently appointed by Prime Minister Boris Johnson to lead U.K. relations with the bloc. “I made clear to them my regret that the U.K. had moved in a unilateral way,” Coveney said.

Frost is due to speak with European Commission Vice President Maros Sefcovic about the issue later Wednesday.

The requirement for export documents on food entering Northern Ireland from the rest of the U.K. was part of the Brexit accord, to ensure that goods crossing into the EU respected its rules and to avoid creating a border on the island of Ireland.

Supermarkets have spoken out against the looming requirement for the export documents, saying it would lead to higher food prices and reduced choice in shops. The unilateral extension is welcome news for businesses, said Aodhan Connolly, director of the Northern Ireland Retail Consortium.

“Retailers and consumers still need the certainty of a long-term workable solution,” Connolly said. “This all must be done with the least disruption to communities in Northern Ireland.”