This week's Brussels summit had been set as the deadline for a draft deal, but European Union leaders have instead been left to contemplate the potentially catastrophic scenario of Britain crashing out in March without any agreement.
His criticism was also echoed by DUP deputy leader Nigel Dodds, who said "to use the prospect of violence and terrorism is a disgraceful and risky gamble".
An aide to Macron said he and Merkel walked back together to their hotel from the summit and when they got there he got a text from Bettel inviting him round the corner for a drink: "It was totally spur of the moment", the aide said.
The stunt was viewed with disgust by many in Northern Ireland, however, with some seeing it as a threat of sorts - particularly given insider claims that elements of the political elite and security establishment in the Republic of Ireland colluded with the IRA when they were at their most active.
To the fury of hardline Brexiters in May's ruling Conservative Party, the biggest takeaway from the Brussels meeting is Britain and its negotiating partners could be heading for many months more of convoluted talks.
Luxembourg Prime Minister Xavier Bettel added that Britain's general approach remained a problem.
She set out the significant progress that has been made on the Withdrawal Agreement and on our future relationship with the EU.More news: Donald Trump Would Prefer To Pick A Woman For UN Envoy
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Over dinner afterwards, they agreed to keep talking, but upped the pressure by refusing to sign off on a planned special summit next month to seal the divorce.
Under the EU's idea of a contingency plan, Northern Ireland would remain in the EU's customs union, large parts of the single market and the EU VAT system - something the United Kingdom says is unacceptable as it would create a new border down the Irish Sea, between Northern Ireland and the rest of the UK.
Bloomberg reported late last week that May is said to be ready to ditch one of her key Brexit demands to resolve the vexed issue of the Irish border and clear the path to a deal.
"This prolongation of the transition period probably will happen", Juncker said. "It is not the best idea the two of us had but it is giving us some room to prepare the future relationship in the best way possible", Juncker added.
Theresa May returns to Westminster on Friday facing one of the most unsafe weeks of her premiership, with Conservative MPs from all sides of the party losing patience in her handling of Brexit.
Brexit supporters in May's government are concerned any temporary arrangements with the European Union that lack a clear time limit may become permanent solutions over time.
"We are building on the 106 technical notices we have published explaining how we will avoid, manage or mitigate the short-term risks of a no deal scenario - and make a success of Brexit". "There are some hard issues we are still working through".
May has tried to use the summit in Brussels - once seen as the stage for a possible breakthrough after more than a year of talks - to offer a softer tone to her European Union counterparts after another such meeting last month ended in acrimony.
"I'm convinced a deal is necessary, I'm still not sure we'll get one", he said.