The UK government on Monday said it stood ready to abandon a post-Brexit trading accord for Northern Ireland soon, unless the EU agreed to wholesale changes.
Speaking at the annual conference of the ruling Conservative party, Brexit minister David Frost said he anticipated a response from Brussels "over the next couple of weeks" regarding the province.
That would then trigger what Frost said should be a short period of negotiations that could lead to the government invoking a suspension clause -- Article 16 -- of the so-called Northern Ireland Protocol.
"Will it be over by Christmas? I think something will be over by Christmas," he said on the conference fringes, referring to the possible triggering of Article 16.
But the UK would give due notice to avoid destabilising Northern Ireland further, he added.
"I assume if we do use Article 16, the EU will look to retaliate" through trade tariffs on UK-wide goods, he added. "I hope they don't.
"The unity of the country is paramount, obviously, and we have to proceed on that basis."
- Business fears -
The British Chambers of Commerce said an "agreed solution" between London and Brussels about the protocol was "by far the best outcome", as it offered businesses certainty.
"The last thing exporters need is the risk of tariffs hanging over UK goods exports to the UK if agreement on the protocol cannot be reached and talks break down," said head of trade policy William Bain.
Northern Ireland Secretary Brandon Lewis told delegates the government wanted "to negotiate a solution that is binding and sustainable".
"The current structure of the Protocol is not sustainable. It is failing everyone in Northern Ireland," he said at an event alongside the territory's former first minister, Arlene Foster.
Foster, relaying the universal loathing of the protocol among pro-UK unionist leaders in Northern Ireland, earned applause from the packed hall in demanding of Article 16: "What are we waiting for?"
In Brussels, EU spokesman Dan Ferrie declined to address the UK threats specifically.
"But you know we're working intensively to find practical solutions to some of the difficulties that people in Northern Ireland are experiencing," he told reporters.
"We intend to come forward with solutions soon."
The protocol formed part of the UK's drawn-out divorce from the EU, and was designed to prevent unchecked goods heading into the bloc's single market via the UK's only land border with the EU to Ireland.
But unionists in Northern Ireland are opposed, arguing checks on goods from mainland Great Britain -- England, Scotland and Wales -- effectively create a border in the Irish Sea, compromising the province's place in the wider UK.
- 'Heavy-handed' -
Frost said there were indications that Brussels was dropping its prior insistence that the protocol is not up for renegotiation, made when he presented a package of proposed reforms in July.
"The long bad dream of our EU membership is over," he also said in an earlier speech to the Conservative gathering.
"The British renaissance has begun," he said, insisting that Brexit was working in recapturing UK sovereignty despite a supply chain crisis roiling the economy.
But for Northern Ireland in particular, trust in the tricky compromises worked out with Brussels had "collapsed", Frost said, blaming the EU's "heavy-handed actions".
Foster said there was widespread evidence of companies diverting trade away from Northern Ireland, which she said would be one of the permissible factors foreseen in the protocol for invoking Article 16.
Nevertheless, Lewis talked up the province's potential as a bridgehead between the UK and the EU's single market, as well as its promise as a hub for the film, technology and medical industries.
"There's so much that Northern Ireland has to offer," he said. "Leaving the European Union and dealing with the Protocol means we can turbo charge that."