Taoiseach Leo Varadkar has told the Dail that the DUP believes the integrity of the United Kingdom is of utmost importance, even if it means a "lesser world".
The Fine Gael leader was addressing TDs on Wednesday as the DUP continue to express grave concerns over Prime Minister Theresa May's draft Brexit withdrawal deal.
The DUP is unhappy that the deal will see Northern Ireland aligned with EU rules and remain part of the single market with checks on some goods coming in from the UK to Northern Ireland, if the Brexit backstop is implemented.
Senior DUP figures have expressed concern that Mrs May's Brexit plan could lead to the breakup of the United Kingdom.
Mr Varadkar told the Dail that the DUP would prioritise the union over the greater good.
"The DUP holds very firm to this view that the most important thing is the integrity of the UK, the integrity of the precious union, and, if that means a lesser world, that's acceptable provided that the integrity of the union is upheld," the Taoiseach.
He added that the draft agreement reached on the withdrawal of the UK from the EU should not be seen by unionists as a threat to the union.
Mr Varadkar said it was a "real shame" that the Northern Ireland institutions were not functioning during what he called "this very significant time".
He said the DUP was a hard-line unionist party, adding that they would not object to being described as such, and said that they were "not well disposed" to taking advice from Irish governments.
The Taoiseach said "nobody knows for sure" what would happen in a no-deal Brexit scenario.
"Nobody knows for sure what would happen in a no-deal scenario where the UK crashed out of the European Union without a deal," he said.
In such a scenario Mr Varadkar said negotiating teams would have to try to agree an arrangement to avoid a hard border.
"Nobody knows how long that no deal would last," he said.
"It's my view that if we did end up in a no-deal situation, we would find ourselves having to negotiate a no-deal deal quite soon thereafter, so it might happen for a few weeks."
The Taoiseach said that he agreed with other parliamentarians that it would be a "disaster".