Peter Robinson has dramatically pulled out of a St Patrick's Day visit to Washington to meet President Obama, in the wake of the latest Stormont crisis, the Belfast Telegraph can reveal.
With the Assembly now facing a real threat to its existence, the First Minister is expected to be in New York today for a series of planned investment meetings, but is due back in Northern Ireland by Thursday.
The Stormont House Agreement now lies in tatters after Sinn Fein withdrew support for welfare reform, and a furious Mr Robinson now has no appetite for the planned trip to the White House alongside Martin McGuinness next week. It was expected they would be lauded by Mr Obama in the Oval Office after last year's presidential snub.
But a senior DUP source said: "Mr Robinson can see no point in going ahead with the Washington visit in the absence of agreement."
The odds of a snap Assembly election are also growing, as the unforeseen dispute threatens to bring the Stormont government down. Writing exclusively for the Belfast Telegraph, Mr Robinson said Sinn Fein were "risking it all", leaving the public wondering why.
"Why, whenever Martin McGuinness and others have robustly defended the deal they did as being a triumph for the vulnerable?" the DUP leader asked.
"Why, whenever the five-party agreement is a publicly available document, are they now turning their back on it?
"And why, whenever the details that Sinn Fein signed up to are printed in black and white, are they trying to renegotiate it all over again?"
"This is not the first time the word 'crisis' has been associated with Stormont. But be in no doubt, Sinn Fein's bad faith will have very serious consequences," he said.
"This will impact on our Budget and could cost us several hundred million pounds.
"The ability to reduce the rate of corporation tax, create jobs and grow our economy will be lost.
"The very existence of Stormont itself could be in jeopardy."
Without a resolution, there is a prospect of an Assembly election in May, possibly alongside the General Election.
Other major repercussions for Northern Ireland include:
In his shock announcement, Mr McGuinness accused the DUP of attempting to introduce Tory welfare cuts "by subterfuge" as his party withdrew support for the welfare legislation - just hours before it was due to pass its final stage.
"The DUP have acted in bad faith and are now reneging on their commitments to protect the most vulnerable. It is their intention to provide only partial protection to current recipients of benefit and no protection whatsoever for future claimants," said the Deputy First Minister.
"That is totally unacceptable. If the DUP want to strip benefits from children with disabilities, from adults with severe disabilities, the long-term sick; or push children further into poverty, then they need to explain and justify that."
Mr Robinson called it the "most dishonourable ham-fisted" statement he had seen in politics. Secretary of State Theresa Villiers warned: "It remains pivotal that all aspects of the Agreement are implemented in full. Failure to make progress on the issue of welfare has serious implications for the Executive.
"The recently agreed 2015-16 Budget will not be deliverable in its current form."
McGuinness on Friday...
We agreed with the DUP and the other Executive parties a package of protection for those who would have faced benefit cuts as a result of welfare reform. Our protected welfare system has eliminated the Tory cuts which are being imposed on the most vulnerable in Britain and which they sought to impose here on our most vulnerable.
Until such times as the minister can produce a scheme for agreement which gives effect to the intent of the Stormont House Agreement by providing full protection for current and future claimants, Sinn Féin will not be in a position to support the Welfare Bill going through the Assembly.
How scared should a unionist be? What chance is there now that power sharing can work? The statement by Martin McGuinness yesterday, announcing that his party would vote against welfare reform, effectively scuppering the Stormont House Agreement which is predicated on it, had a familiar ring to it.