The Irish government has denied threatening to derail the Brexit negotiations but insisted it would remain "resolute" in its stance over the border row with the UK.
Theresa May has just a week to meet a European Union deadline to make progress on key Brexit stumbling blocks, including the handling of Northern Ireland's border, but Cabinet minister Liam Fox said the issue could not be finally resolved until trade talks with Brussels have progressed.
Dr Fox said a final position could not be reached until it was known what the "end state" of the UK-EU relationship will be after the 2019 separation, but Dublin has indicated trade talks could be held up unless firm guarantees on the border are given by the Prime Minister.
Ireland's Foreign Affairs Minister Simon Coveney dismissed a claim from Ukip that Ireland was threatening the UK, but insisted that his country must be protected in the Brexit process.
He said: "Ireland is not threatening anybody, least of all a friend, but we remain resolute in our insistence on a sensible way through Brexit that protects Ireland."
Dublin has said that if either the whole of the UK or just Northern Ireland remains in the single market and customs union then there would be no problem with maintaining the current soft border arrangements - a proposal ruled out by the Prime Minister.
Mrs May has been given until December 4 to come up with further proposals on issues including the border, the Brexit divorce bill and citizens' rights if European leaders are to give the green light to moving on to the next phase of negotiations covering the future trading relationship between the UK and Brussels.
International Trade Secretary Dr Fox said: "We don't want there to be a hard border but the UK is going to be leaving the customs union and the single market."
He told Sky News's Sunday with Niall Paterson: "We have always had exceptions for Ireland, whether it's in our voting rights, our rights of residence in the UK, we have always accepted a certain asymmetry and that will have to be part of whatever agreement we come to with the European Union but we can't come to a final answer to the Irish question until we get an idea of the end state.
"And until we get into discussions with the EU on the end state that will be very difficult, so the quicker that we can do that the better and we are still in a position where the EU doesn't want to do that."
He blamed the European Commission's "obsession" with forging a closer union for the delays in the Brexit talks, which the UK hopes will move on to discussing trade after a meeting of EU leaders on December 14-15.
Irish European Affairs Minister Helen McEntee acknowledged that some of the final details would have to be dealt with in the next phase of Brexit talks but the UK must come forward with further proposals now to achieve the aim of maintaining a soft border.
Progress on to phase two of the negotiations can only happen if all 27 leaders of the remaining EU countries agree "sufficient progress" has been made on the first set of issues.
Ms McEntee told Channel 4 News: "If all of the options that we feel can make that possible have been taken off the table then we need them to produce something else that will give us confidence, moving into phase two, that this can actually be achieved. To date this has not happened."
Any arrangement which appeared to give Northern Ireland a separate status would be strongly resisted by the DUP, whose 10 MPs are effectively keeping Mrs May in Downing Street after she lost her majority in the general election.