European Council President Donald Tusk has warned British Prime Minister Boris Johnson that Brexit is not about "winning some stupid blame game" but what is at stake is the future of Europe and the UK.

In a tweet he added: "At stake is the future of Europe and the UK as well as the security and interests of our people. You don't want a deal, you don't want an extension, you don't want to revoke, quo vadis?".

Tánaiste and Minister for Foreign Affairs Simon Coveney said it was hard to disagree with Mr Tusk's comments but "we remain open" to finalising a fair Brexit deal.

He added that the Taoiseach wants to find a compromise on Brexit that works, but is not willing to be boxed into a corner and accept proposals that are not consistent with the current agreement or the backstop.

Responding to leaks to British media outlets in which it was claimed that Leo Varadkar does not want to reach an agreement, Mr. Coveney said the briefing to UK media was about putting pressure on the Taoiseach.

He said if the approach from the British government is to "take it or leave it" on their latest proposal from last week, then "the British side must know there is not going to be a deal".

The Foreign Affairs Minister said the comment from president Donald Tusk is a reflection of frustration.

European Council President Donald Tusk

Mr Tusk's comments on twitter follow reports that German Chancellor Angela Merkel told Mr Johnson that to do a Brexit deal, Northern Ireland must stay in the European Union's customs union.

With just 23 days to go before the UK is due to leave the EU, the future of Brexit remains deeply uncertain.

EU leaders have reacted coolly to Mr Johnson's last-ditch proposals to bridge the impasse, and while negotiations are ongoing, many diplomats say the chances of a swift deal before 31 October are low.

The Downing Street source said Chancellor Merkel spoke to Mr Johnson this morning and she made clear that a deal was "overwhelmingly unlikely".

She said that for a deal, Northern Ireland would have to stay in the EU's customs union and full alignment with the EU forever, the source said.

Mrs Merkel is said to have told the Prime Minister that Northern Ireland is the UK's "special problem" and that the Republic must at least have a veto on it leaving the customs union.

"If this represents a new established position then it means a deal is essentially impossible not just now but ever," the Downing Street source said.

"It also made clear that they are willing to torpedo the Good Friday Agreement."

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European Commission spokeswoman Mina Andreeva said: "From our side we reiterate that the EU position has not changed. We want a deal, we are working with the UK for a deal.

"Technical talks are continuing today so I don't see how talks could have actually broken down if they are happening today and in the days to continue," she said.

Talks between Mr Johnson's EU negotiator David Frost and junior EU officials will begin later today.

Mr Coveney will meet the EU's chief Brexit negotiator Michel Barnier this evening and tomorrow, Mr Barnier is to brief the European Commission.

Officials have said the talks must lead to a legal text by Friday if they are to be considered at the October 17-18 summit. 

Scotland's First Minister Nicola Sturgeon said the UK government's attempt to shift the blame is "pathetically transparent".

Labour's Brexit spokesperson Keir Starmer said the comments from Downing Street represented a "cynical attempt" by Number 10 to "sabotage" the negotiations.

A spokesman for the German government confirmed that the Chancellor and the Prime Minister had spoken but said he would not comment on the content of the call.

Downing Street refused to comment on where the "Number 10 source" quotes came from regarding the Prime Minister's call with Chancellor Merkel.

The Prime Minister's spokesman said the call involved a "frank exchange" on the progress of the Brexit talks.

"The purpose of the call was to discuss the progress that has been made in the talks so far," he said.

"I would describe it as a frank exchange. The Prime Minister set out that the UK had made what we believe to be a significant offer but if we are to make future progress then the EU will need to compromise itself."

The spokesman for Mr Johnson said the talks were now at a "critical point". 

The PM's spokesman confirmed that the future of Northern Ireland and whether it remained in the European customs union remained an issue.

"The Prime Minister's position is a clear one. The UK needs to leave the EU in its entirety and it is not acceptable for Northern Ireland to be left behind in a customs union," the spokesman told journalists at a briefing in Westminster.

"I don't think the Prime Minister could have been any clearer on that." 

DUP leader Arlene Foster said Chancellor Merkel's comments reveal "the real objective of Dublin and the European Union".

Brexit Party leader Nigel Farage said no British government could accept Germany telling us that part of the UK has to stay in the EU.

Meanwhile, the UK government has released its Brexit "no-deal readiness report" with Mr Johnson insisting he will deliver an EU withdrawal by 31 October.

"I am determined to deliver by the end of this month," he said.

"If we are going to restore faith in our institutions, we must make sure that Britain leaves the EU on October 31."

Mr Johnson unveiled a new plan last week aimed at keeping Britain's border with Ireland free-flowing after Brexit.

It envisages keeping Northern Ireland aligned with the EU's single market regulations, but part of a UK-wide customs territory.

But this would mean customs checks on the Irish border, something the EU has long opposed.

Brexit talks to end this week?

Meanwhile, a Downing Street source has revealed Brexit talks will 'probably end this week'.

Last night, James Forsyth of The Spectator magazine got a scoop - a lengthy response from a Downing Street source to a question on the progress of Brexit talks. 

The memo has been printed in full by the magazine on its website. 

As RTÉ's London correspondent Sean Whelan explained, Number 10 has not disavowed the memo or its central claim - that the British government expects the talks on the British proposals to change the Irish backstop to end this week.

Additional Reporting Fran McNulty, PA