A European Parliament vote in favour of Northern Ireland being granted special status has been welcomed by nationalists but strongly criticised by unionists.
Strasbourg also backed a resolution declaring that negotiations between the EU and the British Government hadn't made sufficient progress to move to the next phase of talks, which will centre on trade.
Welcoming the motion in favour of Northern Ireland remaining in the single market and customs union after Brexit, Sinn Fein MEP Martina Anderson said: "It is a clear indication of the growing support for special status for the North within the EU across Europe.
"This resolution is an important step forward in recognising that the needs of the north of Ireland are different to those of Britain."
However, DUP leader Arlene Foster told Cabinet ministers at a reception hosted by the Conservatives at their annual conference last night that her party would not accept any solution that involved a border being effectively drawn in the Irish Sea.
"We really, really believe in the single market - the single market of the United Kingdom," she said. "That is the one that is most important to us. So all of this talk about a border down the Irish Sea is a complete non-starter to the people and the business community of Northern Ireland."
Earlier, DUP MEP Diane Dodds said: "Let us be clear, Northern Ireland's Brexit solution will be part of the UK's solution.
"There can be no question of a deal that cuts us adrift from our most important market and erects barriers within the UK single market.
"The interlinked nature of the Brexit negotiation means that we need to move swiftly to the second phase of the negotiation for a full resolution.
"Northern Ireland is not a bargaining chip in these negotiations. The genuine concerns in my constituency should not be exploited in pursuit of every British pound."
UUP MEP Jim Nicholson said the EU was no longer impartial in the dispute between unionists and nationalists and was now "essentially calling for an international border to be placed between Northern Ireland and the rest of the UK".
"This is a sad day for me. By backing this text, it feels as though Europe is turning its back on decades of good relations with all communities in Northern Ireland. That is a huge mistake," he added.
But welcoming the resolution, SDLP MLA Claire Hanna said the EU's commitment "to defending the interests of this island, north and south, had remained steadfast".
Alliance deputy leader Stephen Farry said: "The surest way to avoid a hard border is for the UK as a whole agreeing a fresh customs union with the EU."