Northern Ireland's Democratic Unionist Party accused Britain on Tuesday of keeping it in the dark over a proposed Brexit deal on the Irish border but said it would examine the text after blocking an agreement in Brussels.

"The text only came through to us late yesterday morning. Obviously once we saw the text, we knew that it was not going to be acceptable," DUP leader Arlene Foster told Irish public broadcaster RTE.

"Now we need to look at the text, make it clear what we cannot agree with and try to work through all of that because we want to move to phase two as much as anybody else," Foster said, referring to the next stage of UK-EU talks on a future trade partnership.

Foster, whose support in parliament keeps British Prime Minister Theresa May's Conservative government in office, was due to speak with the premier later Tuesday.

European Commission president Jean-Claude Juncker said he would then be meeting May "in the course of this week", either on Wednesday, Thursday or Sunday.

London had reportedly agreed that Northern Ireland, part of the UK, would maintain "regulatory alignment" with EU-member Ireland after Brexit, even as the UK as a whole withdraws from the bloc's single market and customs union.

Dublin had demanded guarantees that Brexit would not lead to the return of frontier checks, which could incite sectarian tensions in a region once plagued by violence.

But as May sought to close the deal over lunch with Juncker in Brussels on Monday, the DUP, Northern Ireland's pro-British biggest party, made clear its opposition.

Foster said that the draft agreement was a "big shock" and she accused the Irish government of pursuing an "aggressive agenda" of Irish reunification.

She also said she had been told by British negotiators that the Irish government had prevented them from sending a draft text to the DUP.

- Left behind? -

Several Conservative MPs have also expressed alarm, with one leading Brexit supporter, Jacob Rees-Mogg, warning "the government doesn't have a majority" to effectively move the EU customs border into the Irish Sea.

Scottish Conservative leader Ruth Davidson said it would be preferable to have regulatory alignment with the EU for the whole UK.

Brexit minister David Davis suggested this could be an option, saying: "The presumption of the discussion was that everything we talked about applied to the whole UK."

Called to make an emergency statement to the House of Commons, however, he repeated that alignment was not the same as the harmonisation of rules, but about achieving similar outcomes.

He said there was no question Northern Ireland might be "left behind" in the EU single market and customs union, reaffirming his commitment to the UK's "territorial integrity".

Without giving more details, he said "we are now close" to an agreement in time for a summit next week, when EU leaders will decide whether to move the negotiations onto trade.

The frenzied diplomacy caused the pound, which had rallied on Monday on hopes of a deal, to fall on the currency markets against the euro and the dollar.

- 'What a shambles' -

May's domestic critics quickly seized on her failure to agree a deal.

"We have a prime minister who is so weak that the DUP has a veto over any proposal she makes," Keir Starmer, Brexit spokesman for the main opposition Labour party, told MPs.

"What a shambles. What a complete mess," said Scottish nationalist MP Peter Grant.

Ireland's ambassador to London, Adrian O'Neill, said the problem would be resolved if Britain stayed in the customs union -- something officials reject, as it would prohibit them from signing external trade deals.

He said there was still scope to reach a deal, but "if it goes beyond this weekend, we may run out of time".

The EU has said there must be progress on three key issues before moving on to trade talks at the summit on December 14 and 15.

Although the question of Britain's financial settlement is largely agreed, differences remain on the role of the European Court of Justice in securing the rights of EU citizens in post-Brexit Britain.

But failure to reach a deal on Ireland could hold up the entire process -- leaving less time for Britain to secure a trade agreement before it leaves the EU in March 2019.

source: AFP