This is the rhetoric ahead of Wednesday's summit.
Other sources familiar with Barnier's meeting with European Union ambassadors confirmed this, and one added that "certain countries insisted that preparations for a "no deal" be accelerated".
The most damning assessment came from French President Emmanuel Macron, who told May that Brexit was sold sold to the British people by "liars (who) left the next day so they didn't have to manage it".
If Britain leaves the European Union without an agreement on future relations, there could be chaos - tariffs would go up on trade, airlines could no longer have permits to fly between the two regions, and freight could be lined up for miles at border crossings as customs checks are restored overnight.
The Irish border is an acutely sensitive issue, with some fearing any return to customs checks and other controls could revive tensions between Northern Ireland's Irish Catholic community and its British U.K. Protestant one. Coveney suggested that May was reneging on part of Britain's commitment, made in December, to ensure that there is no hard border on the island of Ireland. The permanent removal of border infrastructure was an element of the 1998 Good Friday Agreement, which brought peace to Ireland after decades of sectarian conflict. She says that is unacceptable because it would impose new controls between Northern Ireland and the rest of the UK.
May argues this amounts to splitting the United Kingdom into different customs zones, a political nonstarter.
The stubborn problem of Britain's land border with Ireland thwarted a drive to clinch a Brexit deal before a European Union summit this week, as negotiators admitted defeat after marathon talks and pressed pause for the coming days.
Also it is confirmation, if such were needed, of how hard it is for Barnier to drop a solution for Northern Ireland that introduces trade barriers with Great Britain. "Without a clear vote in the European Parliament and without a clear vote in the British Parliament, it won't succeed in the end".
Her words came less than 24 hours after the Brexit talks hit yet another bump, with progress on the so-called "backstop" arrangement for any deal reaching a deadlock in Brussels.
Both sides are now focusing on another summit in November, with the hope that differences can be squared at a further meeting before Christmas.
Citing diplomats familiar with the situation, Bloomberg said the transition extension until the end of 2021 - which would only be enacted if trade talks slowed - would help overcome the last major hurdle in Brexit talks, namely the Irish border issue.
While supporters of Brexit have so far dominated the debate within the Conservative Party, there were calls from members of its pro-EU wing to avoid a hard exit and retain numerous benefits membership of the bloc brings the UK.
"We will take this time, calmly and seriously, to find this global agreement in the next weeks", he said.
Opposition Labour leader Jeremy Corbyn blasted May's approach, saying "the Prime Minister's failure to stand up to the warring factions on her own side have led us to this impasse".
During a recent appearance on Good Morning Britain, Johnson championed Margaret Thatcher's policies towards Northern Ireland and argued that Thatcher would be happy letting "the Irish shoot each other" - regardless of there being a hard/soft border.