According to a report from the UK's Observer on Sunday, the DUP has been preparing for a "no deal" Brexit as the most likely outcome, as May's negotiators continued to pursue a deal on the Northern Ireland issue.
"We were actually pretty hopeful that we would manage to seal an exit agreement" but "at the moment, it looks a bit more hard again", the German chancellor told the German Foreign Trade Federation of the latest talks, which have largely been held in secret.
Tusk added: "But let me be absolutely clear".
Ms. May's backing away from a deal that was close to being agreed on, follows growing pressure from within her party.
"This is what our state of mind should be at this stage".
"We are not going to be stuck in single customs territory unable to do meaningful trade deals", a spokesman for May said on Monday.
The EU today threatened to scrap a special November summit of EU leaders that was meant to finalise the Brexit deal.
The EU has proposed a backstop that would mean Northern Ireland staying in the customs union, large parts of the single market and the EU VAT system - the United Kingdom has rejected this, instead proposing a backstop which would effectively keep the whole of the United Kingdom in the EU customs union for a limited period.
Despite the tough comments, European Union officials insisted that the negotiations had been merely been put on "pause" rather than having suffered a breakdown.
Cabinet ministers are assembled in Downing Street this morning as the prime minister faces a cabinet meeting, with Brexit the main item on the agenda.
Second, explained the PM, she should be able to promise the British people that the backstop is only a temporary solution, which won't become "a permanent limbo". If there is any time, any window of opportunity for people to think and come up with rival ideas, then any compromise is surely doomed.
While the European Council admitted that "clearly we are not in the place we wanted to be". "We are still positive we can achieve it, so there's no reason to despair". Ex-Brexit secretary David Davis called on current members of the government to rebel against May's plan, while ex-foreign secretary Boris Johnson has said that if implemented, it would amount to the greatest "national humiliation" in over 60 years.
However, hopes of that happening were dealt a major blow on Sunday when ministers failed to make anticipated progress on the Irish border problem.
Brexit talks hinge on how those promises are interpreted.
The EU has also repeatedly refused to allow the backstop proposal to be time-limited.
Given all of this, we can only conclude that May is deliberately running out the clock: even if progress is made in the next few weeks, there will be little public noise in that direction.
He also said the fact that the European Union is preparing for a no-deal scenario "must not, under any circumstances, lead us away from making every effort to reach the best agreement possible" for all involved. "Whether we do this week or not, who knows?"