The U.K. wants the European Union to extend grace periods for trade between Northern Ireland and Great Britain until 2023, according to a letter from Cabinet Minister Michael Gove to the bloc seen by Bloomberg.

The government will “use all instruments at its disposal” if the EU doesn’t satisfactorily address the issues on the flow of trade, Gove tells European Commission Vice President Maros Sefcovic in the letter. The pair are scheduled to hold a meeting on Wednesday with the first minister and deputy first minister of Northern Ireland.

The grace periods relate to difficulties in implementing parts of the Brexit deal aimed at keeping an invisible border between the Irish Republic and Northern Ireland, which remains in the EU’s customs union and single market.

This issue was given extra urgency last week when the European Commission announced it would activate an emergency trigger to control exports of vaccines to Northern Ireland. A few hours later, it admitted that it was wrong to have done so, and reversed its decision.

In the letter, Gove describes the earlier move as a “grave error,” adding “the feelings of disappointment were particularly acute given the concerns that had already arisen about the practical operation of the Protocol and its economic and societal effects.”

Officials from the EU and the U.K. have temporarily halted some checks at the region’s ports after what Mid & East Antrim Council called “an upsurge in sinister and menacing behavior.”