German Chancellor Angela Merkel has revealed Germany has begun planning for a no-deal Brexit as Prime Minister Theresa May arrives in Brussels for critical last-minute talks.

Earlier, President of the European Council Donald Tusk said there was “no optimism” for a deal on the Irish border, with Mrs May sticking to her Chequers plan and the EU demanding more concessions.

The German Chancellor commented Wednesday afternoon, saying her government had started to make “suitable preparations” for the possibility of the UK and the EU failing to agree on a deal, The Guardian reports.

“It is only fitting as a responsible and forward-thinking government leadership that we prepare for every scenario – that includes the possibility of Great Britain leaving the European Union without an agreement,” she added.

Brexiteers led by Jacob Rees-Mogg say a “no deal” Brexit would not be a bad outcome, although they and pro-Brexit former foreign minister Boris Johnson favour a free trade deal similar to Canada.

Mrs May, meanwhile, has said her Chequers plan is the only option, threatening a general election if it fails and claiming “no deal” is better than a Canada-style deal.

Merkel was speaking to German parliamentarians in a special address dubbed her “big Brexit speech” by the German media, ahead of Wednesday’s European Council meeting.

She demanded more reassurances on issues including citizens’ rights and customs issues, which she insisted remain unresolved.

“This brings with it a whole array of questions, such as: how, the day after Brexit, do we manage the estimated 100,000 British citizens who, in some cases, have been living in Germany for years?

“How do we deal, for example, with teachers of British citizenship, who are classed as German civil servants, and how should that continue?

“How do we appropriately prepare our authorities for the added burdens to do with customs issues?” she asked.

Merkel said there was an “unfortunate” lack of breakthrough over the Irish border and Mrs May admitted “divisions” remained on the issue as she arrived in Brussels.