The UK government has warned that the special Brexit arrangements for Northern Ireland as they stand are unworkable, in an intervention made at a sensitive phase in talks with the EU on the controversial border checks.

After a visit to meet business leaders in Belfast on Tuesday, the Brexit minister, Lord Frost urged the EU to take a pragmatic approach in talks.

And he warned that the UK would “continue to consider all our options” in relation to the protocol, which in the past has included unilateral action to suspend it in part.

“It’s clear from my visit that the protocol is presenting significant challenges for many in Northern Ireland. Businesses have gone to extraordinary efforts to make the current requirements work, but it is hard to see that the way the protocol is currently operating can be sustainable for long.

“We’re committed to working through the issues with the EU urgently and in good faith. I hope they will take a common sense, risk-based approach that enables us to agree a pragmatic way forward that substantially eases the burdens on Northern Ireland,” he said in a statement.

While the UK has repeated its support for the protocol since violence broke out in loyalist communities, Frost’s statement suggesting he believes there is more scope for movement on the Brussels side in relation to dropping some of the checks on supermarket food and plants that unionists see as an attack on the union between Northern Ireland and Great Britain.

But Brussels sources insist the talks “are not negotiations” as the protocol is a direct consequence of the hard Brexit Boris Johnson had opted for.

Diplomatic sources say that the UK has ruled out the most helpful option of aligning food standards with those of the EU.

This could have seen a reduction of about 90% of documentary checks and 98% of physical checks conducted at the border, according to recent select committee evidence from Shanker Singham, one of the government’s key advisers in the Brexit negotiations on the Irish border question.

Talks aimed at finding a path to minimise the checks, which led to tensions and violence in loyalist communities, have been ongoing for weeks.

But agreement has only been reached on a handful of items including waivers for guide dogs and for pedigree livestock crossing the Irish Sea.

Talks are now centring on the potential for checks exclusively on food and other goods going into Northern Ireland from Great Britain which are considered “at risk” of crossing the border into the republic.

Under the withdrawal agreement, Northern Ireland is observing the EU rules on food and although the UK follows the same rules, there has been strong political resistance to formalising alignment as it would be seen as a breach of the clean-break from EU law.

Experts have also suggested a food standards agreement similar to that operating between New Zealand and Australia.

Insiders in Brussels say this has not been requested by the UK, and in any case it would not be “a silver bullet” as it covers individual products rather than the broad range of food that crosses the Irish sea.