Hopes are fading for an emergency summit to agree a Brexit deal this month as Downing Street admitted "substantial issues" are still to be overcome between London and Brussels.
Senior British officials were locked in talks until 2.45am with their EU counterparts but failed to produce a decisive breakthrough on the remaining problems, including the vexed issue of the Irish border.
The absence of progress has plunged Theresa May's plans into chaos, as she had hoped to reach an agreement with the EU by Wednesday - the deadline for arranging an emergency EU summit in November.
It also ramps up the need for the UK to make large-scale no-deal Brexit preparations and casts doubt over the ability to pass the right legislation before the official exit day in March 2019.
The delay means cabinet ministers will not discuss whether to sign off the deal at the regular cabinet meeting on Tuesday, although Brexit will be on the agenda.
Downing Street said that there were "substantial issues still to be overcome" in relation to the so-called backstop measure aimed at preventing a hard border between Northern Ireland and Ireland.
The prime minister's official spokesman said: "We have made good progress in the negotiations in relation to the withdrawal agreement but there are substantial issues still to be overcome in relation to the Northern Irish backstop."
The spokesman added: "We want to make to progress as quickly as possible in these negotiations but we have also said that cannot be at any cost. That remains the position."
Meanwhile Michel Barnier, the EU's chief Brexit negotiator, told European leaders that at a meeting of the general affairs council that key issues remained unresolved.
As they gathered for the update, several EU member states claimed that any Brexit deal hinged on agreement of the cabinet, rather than difficulties with Brussels.
Ireland's deputy prime minister Simon Coveney said it was "a very important week for Brexit negotiations," adding that there was "still clearly work to do" to reach an agreement.
His French counterpart Nathalie Loiseau said: "The ball is in the British court. It is a question of a British political decision."
Ms May is facing opposition from all sides over her call for a backstop measure that would keep all of the UK within a customs union, rather than the Northern Ireland-only provision proposed by the EU.
International Development Secretary Penny Mordaunt, who has failed to offer public support to Ms May's blueprint, suggested the Cabinet would act as a "check" on the prime minister.
The Brexiteer told Sky News: "The important thing is that there are two checks on this deal - there is Cabinet and there is Parliament.
"Cabinet's job is to put something to parliament that is going to deliver on the referendum result."
However the PM's spokesman said the cabinet had supported Ms May so far and was expected to continue to do so.
Ex-transport minister Jo Johnson revealed that he chose to dramatically resign from the government last week over reports Ms May was planning a publicity campaign showing a binary choice between a no-deal exit and Ms May's deal - which he said amounted to a "calculated deceit".
"I challenge the government to come clean on the cost of Brexit," he told the Evening Standard.
"The reason they can't look us in the eye, it's because they know this will leave us worse-off and with less control. It's a gross abuse of civil service impartiality."
Mr Johnson added: "There is a sea-change in mood among my Conservative colleagues who are focused by this crisis. I would not be surprised if more colleagues in senior positions speak out."
His brother, the former foreign secretary Boris Johnson, claimed Ms May is on the brink of "total surrender" to the EU over Brexit and told ministers to "mutiny" against the plans.
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