LONDON — The EU is "not interested in the blame game," chief Brexit negotiator Michel Barnier said Friday, as he spelt out legal reassurances offered to the U.K. in recent days.

The unexpected précis of the EU's negotiating position came in a series of tweets from Barnier, just hours after British Prime Minister Theresa May urged the EU in a speech to do more to help her win the support of the House of Commons for the Brexit deal in a crunch vote next Tuesday.

May said the EU has to "make a choice" and that now is "the moment for us to act." But EU negotiators appeared riled by the suggestion of inaction on their part.

Barnier's move, spelling out the EU's take on specific items in active negotiations with London's team is highly unusual and a sign that he is unwilling to cede control of the narrative surrounding the talks. Brussels is keen to show that it is not simply batting back U.K. proposals but is proposing solutions of its own — in the process rebutting the "inflexibility" charge that is often levied by London.

Barnier briefed EU27 ambassadors on the status of talks with the U.K. shortly after May's speech. Emerging from the meeting, he told the BBC: "The EU stands united. We are not interested in the blame game. We are interested in the result. We are still working."

“With a very real deadline looming, now is not the time to rerun old arguments. The U.K. has put forward clear new proposals. We now need to agree a balanced solution that can work for both sides” — Brexit Secretary Stephen Barclay

In the series of tweets, he said the EU had proposed a new, legally binding "interpretation" of the Brexit deal that would bind the EU, were the controversial Northern Ireland backstop to come into force, to use "its best endeavors" to replace it with an alternative arrangement.

A new legal interpretation of the Withdrawal Agreement would also make clear that the U.K. could unilaterally withdraw from the U.K.-EU "single customs territory" envisioned in the backstop, the legal guarantee for avoiding a hard border between Northern Ireland and the Republic of Ireland. That offer came with the significant caveat, though, that the other elements of the backstop would have to remain.

One senior diplomat from an EU27 country said Barnier’s explanation of the EU position on Twitter was an effort to display a "constructive" approach. “The EU has to be constructive till the very end — trying to find suitable solution,” the diplomat said.

“The tweet is probably to pre-empt the expected blame game should [the] Tuesday vote [on the Brexit deal in the House of Commons] fail ... to show that the EU side tried” said a second senior diplomat.

Since the Brexit deal was defeated in the Commons by 230 votes in January, the U.K. has been seeking changes to the backstop to make it more palatable to Brexiteer Conservative MPs and the Northern Irish Democratic Unionist Party (DUP), whose 10 MPs prop up May's government. Brexiteers' key demands have been a legally binding time limit or a unilateral exit clause from the arrangement as a whole, to ensure the U.K. is not locked indefinitely in a customs union with the EU.

While some Tory Brexiteers might be cheered by further assurance that the U.K. could drop the customs element of the backstop, the substance of the EU's proposals — offered in talks since May's last visit to Brussels on February 20 — is unlikely to allay concerns, in particular those of the DUP, about the nature of the backstop.

Barnier said the EU "commits to give UK the option to exit the Single Customs Territory unilaterally, while the other elements of the backstop must be maintained to avoid a hard border. UK will not be forced into customs union against its will."

The pledge appears to amount to an option for the U.K. to revert to the original version of the backstop proposed by the EU last year. That would have meant Northern Ireland alone remaining within the customs territory of the EU.

This was rejected out of hand by the U.K., because it means erecting an economic border between Northern Ireland and the rest of the U.K. British negotiators pushed instead for the entire U.K. to be, under the backstop, in a single customs territory with the EU to reduce the extent of checks on trade crossing the Irish Sea.

The U.K. government reacted negatively to Barnier's proposals. Brexit Secretary Stephen Barclay said: “With a very real deadline looming, now is not the time to rerun old arguments. The U.K. has put forward clear new proposals. We now need to agree a balanced solution that can work for both sides.”

Barnier’s resurrection of the Northern Ireland-only backstop proposal also brought a scathing response from the DUP. Nigel Dodds, the party’s leader in Westminster, said it is “neither a realistic nor sensible proposal” and accused the EU of “intransigence.”

“It disrespects the constitutional and economic integrity of the United Kingdom. This is an attempt to get ahead of a possible blame game and appear positive when in reality it is going backwards to something rejected a year ago,” he said.

Henry Newman of the Open Europe think tank called it a "non-concession."

In a confirmation that Barnier's tweets did not mark a departure from the EU's position, a "Lines to take" document distributed to ambassadors at Friday's meeting, obtained by POLITICO, states: "To be clear, all of this is fully consistent with the agreed Withdrawal Agreement which will not be reopened." The document states that the EU27 are "open to further, workable ideas from the UK."

Barnier also said that reassurances on the temporary nature of the backstop set out in a January 14 letter to May from European Commission President Jean-Claude Juncker and European Council President Donald Tusk could be granted "legal force" through what he called a "joint interpretative statement," a proposal reported by POLITICO last month.

And Barnier emphasized that, under the terms of the Withdrawal Agreement, the U.K. already has the right to a "proportionate suspension" of its legal obligations to abide by the backstop, if the EU were to fail to negotiate an alternative way of avoiding a hard border. That could only happen, though, if a joint arbitration panel set up by the Withdrawal Agreement ruled in the U.K.'s favor in such a dispute.

The "Lines to take" document states that technical level discussions "will continue over the coming days" but "political level meetings are to be confirmed."

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