At the heart of Tuesday's political drama was an early morning phone call from German Chancellor Angela Merkel to Johnson, regarding the UK's suggestion to have two borders around Northern Ireland - turning the existing (invisible) border with the Republic of Ireland, an European Union member, into a formal customs border (albeit with physical checks and infrastructure some distance from the border itself), with a regulatory border in the Irish Sea, allowing Northern Ireland to remain in the EU's "single market". The chancellor's spokesman declined to comment on "confidential conversations".
The EU hit back with unusually strong language.
Amid frantic diplomatic manoeuvring in European capitals, details of a call earlier on Tuesday between the United Kingdom and German leaders have reignited tensions across the continent.
"Downing Street say Merkel said to Boris Johnson: "Your plan is never gonna work", said Al Jazeera's Laurence Lee, reporting from London.
Varadkar said Ireland can't accept a deal at any cost as Britain seeks to renegotiate plans meant to ensure there is no hard border between the Republic of Ireland and the U.K.'s Northern Ireland.
There was "skepticism" within European Union circles over the U.K.'s description of Johnson's call with Merkel, CBS News partner network BBC News reported.
"Boris Johnson, what's at stake is not winning some stupid blame game", he wrote on Twitter.
However, the two leaders are expected to meet for further Brexit talks later this week.
This, the source said, marked a shift in Germany's approach and made a negotiated deal "essentially impossible".
A frustrated Mr Tusk accused Britain of playing with "the future of Europe and the UK" with no clear plan of what the country wanted.
The Financial Times turns the spotlight on the relationship between UK PM Boris Johnson and Irish leader Leo Varadkar.
"But the real outrage is the German suggestion that Northern Ireland be separated from the UK", Banks said.
The UK's chief negotiator, David Frost, is continuing to meet European Union counterparts in Brussels, but the No 10 source said Tuesday morning's phone call had been a "clarifying moment", adding: "Talks in Brussels are close to breaking down".
"We went too far on this one and apologise unreservedly", Leave.EU spokesman Andy Wigmore said by telephone.
The Spectator magazine quoted an unidentified source in Downing Street as saying that Britain would take an aggressive stance towards the European Union if Brexit talks break down, possibly even by withholding security cooperation.
How people and goods will move across the Irish border is the main sticking point in a deal.
After the UK failed to leave the bloc on 29 March, due to the withdrawal deal being voted down by UK lawmakers, the European Council gave the country an extension until 31 October, with an option to leave earlier if the UK parliament passes the deal. Johnson responded by saying that condition, together with the EU's unwillingness to engage with his latest proposals, paved the way to a no-deal Brexit.
Parliament is set to be suspended later Tuesday so that a new session can begin next week with a major policy speech from Mr Johnson's Conservative government.
One source in Mr Johnson's office told The Spectator magazine the government will try to "do all sorts of things" to prevent another Brexit delay should negotiations really collapse.