The German Chancellor Angela Merkel has told British Prime Minister Boris Johnson a Brexit deal is "overwhelmingly unlikely", according to Downing Street.
Mr Johnson spoke with Ms Merkel for 30 minutes on Tuesday morning, with Mr Johnson stressing that Brexit negotiations in Brussels "are close to breaking down".
An EU-UK agreement is "essentially impossible not just now but ever" following the "clarifying" phone call, a Downing Street source added.
Mr Johnson also expressed his view that some in the EU are hoping a second referendum will reverse Brexit, but told Ms Merkel this will not happen.
Reacting, European Council President Donald Tusk warned Mr Johnson that "what's at stake is not winning some stupid blame game".
In a tweet directed at Mr Johnson, Mr Tusk said: "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?"
The Tánaiste Simon Coveney said it was "hard to disagree" with Mr Tusk's comments.
He added on Twitter: "Reflects the frustration across EU and the enormity of what's at stake for us all. We remain open to finalize a fair #Brexit deal but need a UK Govt willing to work with EU to get it done."
Hard to disagree - reflects the frustration across EU and the enormity of what’s at stake for us all. We remain open to finalize a fair #Brexit deal but need a UK Govt willing to work with EU to get it done. https://t.co/5tUvb6m2K4
— Simon Coveney (@simoncoveney) October 8, 2019
Speaking in Dublin, Mr Coveney said nobody that wants a Brexit deal more than Ireland - but the EU cannot just give the UK what it wants.
"We cannot respond to an approach that says 'give us what we want or we're leaving with a no-deal and everybody gets damaged'.
"This has to be on the basis of a negotiation where the extent of the problems that are caused by Brexit are recognised - particularly on this island.
"The complexity of those challenges are really difficult to respond to".
The news also prompted a new sell-off in the pound sterling.
It was trading more than half a cent lower against both the dollar and the euro - at $1.22 and €1.11 - as a recent rally, on market hopes of a Brexit deal, evaporated.
A Downing Street source said the call between Mr Johnson and Ms Merkel was a "very useful clarifying moment in all sorts of ways", with the result that "a deal is essentially impossible not just now but ever".
"The call with Merkel showed the EU has adopted a new position.
"She made clear a deal is overwhelmingly unlikely and she thinks the EU has a veto on us leaving the customs union.
"Merkel said that if Germany wanted to leave the EU they could do it no problem, but the UK cannot leave without leaving Northern Ireland behind in a customs union and in full alignment forever.
"She said that Ireland is the government's special problem and Ireland must at least have a veto on Northern Ireland leaving.
"Merkel said that the prime minister should tell Northern Ireland that it must stay in full alignment forever, but that even this would not eliminate customs issues.
"It was a very useful clarifying moment in all sorts of ways. If this represents a new established position, then it means a deal is essentially impossible not just now but ever.
"It also made clear that they are willing to torpedo the Good Friday Agreement."
A spokesperson for the German government confirmed Ms Merkel spoke on the phone with Mr Johnson, but said they would not discuss a "confidential conversation".
Meanwhile, the DUP MP Sammy Wilson has claimed the Irish Government is adopting a "Dublin says no" policy in the Brexit negotiations.