British Brexit minister David Frost said on Monday that the European Union’s proposals to solve the problem of trade involving Northern Ireland did not go far enough and significant gaps remained between the two sides.

The two sides are in negotiations to find a common solution to issues with the part of a Brexit deal that governs trade between Britain, British province Northern Ireland, and EU member Ireland.

Earlier this month, the European Union presented proposals to fix those issues.

“The problem with them is that they don’t go far enough. I’m not sure they would quite deliver the kind of ambitious, free … trade between Britain and Northern Ireland we would want to see,” Frost told a parliamentary committee.

“It (the discussion between the two sides) has been quite constructive so far but the gaps between us remain significant,” he said.

Goods moving between Britain and Northern Ireland currently face customs checks, as part of a deal to avoid contentious border checks between Northern Ireland and the Irish Republic which could upset peace in the region.

Britain and the EU disagree over how to implement customs and safety checks, which fall especially heavily on meat, dairy and medical products. Britain also objects to the role played by the EU’s supreme court in policing the deal.

Britain has threatened to take unilateral action if a negotiated solution cannot be found, but Frost said he would give the current round of talks a chance to succeed.

“We all see this as an issue for the autumn, to be settled one way or the other,” he said. “We will try everything, and we are trying everything, and exploring every avenue.”

He declined to give further details on how or when Britain would use so-called Article 16 provisions in the deal to take unilateral action.