As the rhetoric from Belfast intensifies and the DUP doubles down on its opposition to any checks on trade between Britain and Northern Ireland, Sabine Weyand, the deputy to the chief negotiator, Michel Barnier, told a delegation of Northern Irish business leaders invited to Brussels this week that the deal on the table was "the best the European Union has ever offered any country in the world".
The Democratic Unionist Party (DUP) is the other big issue for the prime minister, who relies on the Northern Irish party's votes to give her a notional majority in parliament.
Brussels has proposed a backstop that would see Northern Ireland staying in the EU customs union - something the United Kingdom says would create a border down the Irish Sea.
The Irish backstop measure, created to ensure no new border emerges between Ireland and Northern Ireland, is supposed to be temporary until a UK-EU trade deal can be agreed, and Theresa May pledged earlier this year that the arrangement would expire "at the very latest by the end of December 2021".
"These are significant days for Northern Ireland and the United Kingdom as we know it", she said.
Red lines: DUP leader Arlene Foster in Brussels.
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The British government and leading politicians in Northern Ireland insist they will not agree to a withdrawal treaty that foresees the possibility of Northern Ireland being kept inside the EU's economic area while the British mainland is not.
Brexiteers are particularly anxious that Britain could be tied to European Union mechanisms indefinitely, hindering the country's ability to strike independent trade deals after it has left the bloc. 'An terrible lot depends on the talks in the coming days'. Up to 80 Tories are also reportedly considering voting it down.
The 27 states remaining in the bloc hope to announce "decisive progress" in divorce talks at an European Union summit next week and then finalise their offer of close future ties with Britain next month.
"But that's not a question for us, we're not members of the Conservative Party".
"She will not have DUP support regardless of whether the government tries to bribe, bully or browbeat us into accepting it", Wilson also said. "I think Brexit brings no added value, this is a negative negotiation, it is a lose-lose game, where nobody stands to win", Barnier said in the speech that was met with a standing ovation from small business leaders. She needs to keep either her own party onside or attract votes from the main opposition Labour Party. Can all three ever be satisfied with the terms of a Brexit deal?
For customs and VAT, Barnier said, "we propose using the existing customs procedures to avoid doing checks at the transit points".