DUP leader Sir Jeffrey Donaldson is set to have a crunch meeting with Foreign Secretary Liz Truss next week over the Northern Ireland Protocol.
It comes as several months of talks between the UK Government and EU over the post-Brexit arrangements have failed to reach a conclusion.
Unionists are strongly opposed to a slew of checks at Northern Ireland’s ports while the region effectively remains within the EU single market, to avoid a hard border with the Republic of Ireland.
Sir Jeffrey has threatened to withdraw his party’s ministers from the Stormont Executive if the UK Government does not act.
Speaking to reporters in Enniskillen, Co Fermanagh on Friday morning, Sir Jeffrey said he has given “time and space” for negotiations but warned the situation “cannot go on indefinitely”.
He said: “Our position has been clear and if agreement cannot be reached quickly, and I have given time and space for these negotiations, I paused the actions that I intended to take when I saw that the EU and the UK Government were coming together to negotiate, I have tried to give time for those negotiations to make progress, but this cannot go on indefinitely.
“We’re now six months on from the UK Government’s command paper where they said six months ago that conditions had been met to trigger Article 16,
“And six months later, nothing has happened. That is not a sustainable position and if the UK Government isn’t prepared to act, I am.”
He said it will “help to determine the direction in which the Government is travelling”.
He added: “Is there, as Liz Truss says, still a commitment to trigger Article 16 if agreement can’t be reached with the EU?
“That’s what she is saying publicly and I want to test that. I want to explore with her what that means, and particularly, what is the time scale for triggering Article 16 if these talks, as it appears at the moment, are not going to be successful?”
Sir Jeffrey said he wants to see Stormont continuing to deliver but he needs an outcome on the protocol talks.
“I know that people will say, ‘But you said that in December’.
“I have tried to be reasonable, I have given time and space for these negotiations, I have waited to see what happens.
“I will talk to Liz Truss and see what she has to say and then we will have to make a judgment as to whether we believe the UK Government is going to deliver on the commitment they made to safeguard Northern Ireland’s place within the UK internal market or not, and if they’re not, then they have dishonoured the agreement which formed the basis on which Stormont was restored and that is not a sustainable position.”
Sir Jeffrey said that, in the absence of his party’s ministers, arrangements will be in place for decisions to be taken on key departmental issues.
“I am not in the business of removing from Northern Ireland the ability to take decisions that benefit the people of Northern Ireland,” he said.
“I want departments to be able to continue taking those decisions, particularly in areas like health and education so we will make provision for that, but we are also clear that we can’t continue in a situation with an executive that was formed on the basis of an agreement that was to protect our place in the UK internal market.
“That has not been delivered and in the absence of delivery on that, then we do not believe it is sustainable to continue unless the UK Government honours their commitment.”