EU leaders are set to organise an emergency Brexit summit in Brussels for November in a last-ditch bid to avoid a no-deal.

President of the European Council Donald Tusk warned that failure to reach a deal would be a “catastrophe” and was still “quite possible” ahead of a meeting this week in Salzburg set to be attended by Theresa May and other national leaders.

In a letter to heads of state and government inviting them to the Salzburg meeting, Mr Tusk floated the possibility of a special November summit, telling them: “Let me recall that limiting the damage caused by Brexit is our shared interest. Unfortunately, a no-deal scenario is still quite possible. But if we all act responsibly, we can avoid a catastrophe.”

EU leaders will on Thursday meet over lunch in the Austrian alpine fortress city with their chief negotiator Michel Barnier and hash out a unified position on Chequers and the future relationship between the EU and UK.

Member states have differences on how much detail they want Britain to commit to in the future relationship by the end of talks to get a deal. Some governments are happy to remain vague in order to ease the passage of a deal – but others, such as France, have concerns that further kicking the can down the road would be ultimately unproductive.

“There are still differences of approach on a few fundamental issues,” one senior EU diplomat said. The diplomat added that member states were divided on whether the declaration “leaves a certain space” for future negotiations on trade and “how detailed it should be”.

Well-connected sources in Brussels have told The Independent that leaders are searching for positive things to say about the PM’s Chequers plan so as not to destabilise her. But they are extremely unlikely to agree to the fundamental proposals on customs and the single market for goods – viewing them as a breach of EU sovereignty and integrity.

Unfortunately, a no deal scenario is still quite possible Donald Tusk, European Council president

Instead, they are likely to emphasise what they see as positive aspects on security and the fact that both sides want a free trade agreement – points that have never been particularly contentious with either side.

“I think the debate on the joint political declaration will take as its point of departure the assessment of the European Commission of progress in negotiation and also the assessment by the commission of the Chequers proposals,” the senior EU diplomat said.

But speaking in Brussels ahead of a meeting of EU ministers, Brexit minister Lord Callanan called for the EU to give ground.

“The UK has compromised, we’ve produced our white paper, and it’s now time for the EU to reciprocate," he told reporters. "If we’re to put together a deal, there has to be compromises from both sides, and we look forward to saying what the EU has to say about this.”

The 27 leaders are also expected to re-state their position on Northern Ireland and their demand that Theresa May agrees to a “backstop” to prevent a hard border. Sources in Brussels suggest the European Commission is drawing up a new plan for the backstop in a bid to win Britain over, but it is unclear what form it will take and whether it will be acceptable to eurosceptics in the Tory party.

Many, including the DUP, on which Theresa May’s minority government relies for a majority in the Commons, view the current plan to keep Northern Ireland in the EU customs area as a breach of British sovereignty.

“Since we are approaching the last lap of the negotiations there is a need to plan that process ahead,” one senior EU diplomat said.

Brexit so far: in pictures Show all 53 1 /53 Brexit so far: in pictures Brexit so far: in pictures Brexit campaign Boris Johnson led the VoteLeave campaign PA Brexit so far: in pictures Brexit campaign Boris Johnson MP, Labour MP Gisela Stuart and UKIP MP Douglas Carswell address the people of Stafford in Market Square during the Vote Leave Brexit Battle Bus tour on 17 May 2016. Their lead line on the tour was: “We send the EU £350 million a week, let's fund our NHS instead.” Getty Brexit so far: in pictures Voting day A man shelters from the rain as he arrives at a polling station in London on 23 June 2016. Millions of Britons voted in the referendum on whether to stay in or leave the European Union AFP/Getty Brexit so far: in pictures Referendum results Leader of Ukip, Nigel Farage, reacts at the Leave EU referendum party at Millbank Tower in central London as results indicated that it was likely the UK would leave the European Union AFP/Getty Brexit so far: in pictures Protesting the result A young couple painted as EU flags and a man with a sign reading “I’m not leaving” protest outside Downing Street against the voters decision to leave the EU on 24 June 2016 Getty Brexit so far: in pictures David Cameron resigns British Prime Minister David Cameron resigns on the steps of 10 Downing Street on 24 June 2016 after the results of the EU referendum were declared and the United Kingdom voted to leave the European Union Getty Brexit so far: in pictures Theresa May Becomes the new Conservative Party leader Theresa May receives a kiss from her husband Philip, after becoming the new Conservative Party leader on 11 July 2016. 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Getty Brexit so far: in pictures People's Vote march As the People's Vote campaign and The Independent's Final Say campaign gain traction, 700,000 people turn out in London to demand a final say on the UK's Brexit deal on October 20 2018 PA Brexit so far: in pictures More resignations As the Prime Minister settles on a Brexit deal, Brexit secretary Dominic Raab resigns along with Work and Pensions secretary Esther McVey and many other ministers Getty Brexit so far: in pictures Final Say petitions delivered to Downing Street People's Vote supporting MPs Chukka Umunna, Justine Greening and Caroline Lucas and The Independent editor Christian Broughton deliver over a million signatures in favour of a People's Vote to the Prime Minister at 10 Downing Street on December 3 2018 PA Brexit so far: in pictures May delays vote On December 10, the Prime Minister delayed the vote on her Brexit deal as it was near certain not to pass through the Commons due to Tory rebels and lack of DUP support AFP/Getty Brexit so far: in pictures No confidence motion Tory MPs triggered a confidence vote in the Prime Minister on December 12. 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The prime minister did not appear in parliament to see another defeat PA Brexit so far: in pictures Labour and Conservative MPs resign and create the Independent Group Back row of Chris Leslie, Gavin Shuker, Chuka Umunna and Mike Gapes, middle row of Angela Smith, Luciana Berger and Ann Coffey and front row of Sarah Wollaston, Heidi Allen, Anna Soubry and Joan Ryan PA Brexit so far: in pictures Non-biding votes on amendments to Brexit motion On February 27 he house held a series of votes, unanimously calling for the UK and EU to guarantee citizens rights in a no-deal scenario AFP/Getty Brexit so far: in pictures Attorney General publishes legal advice A hammer blow for May as Geoffrey Cox said her renegotiated deal can still leave UK in backstop against its will. Mr Cox did say the prime minister’s efforts had reduced the risk of the UK being trapped in the backstop indefinitely. MPs went on to vote against her deal by 391 to 242 UK Parliament/PA Brexit so far: in pictures No-deal off the table MPs rejected a no-deal Brexit by 43 votes on March 13, with cabinet ministers rebelling in another humiliating defeat for Theresa May. A day later they voted in favour of the prime minister seeking an extension to Article 50 AFP/Getty Brexit so far: in pictures House speaker bans May from third Commons vote on same Brexit deal John Bercow sensationally told Theresa May he would stop her making another attempt to pass her Brexit deal unless she has secured changes. The Speaker said a further ‘meaningful vote’ would be ruled out of order if the motion was “the same or substantially the same’ – under an ancient convention to stop the government bullying parliament on issues MPs have rejected Parliament Live Brexit so far: in pictures May writes to Tusk The prime minister wrote to Donald Tusk, president of the European Council, to ask for a three-month extension to give her more time to try to get her deal through parliament. However the European Commission advises the EU27 should offer a short extension to May 23 or a longer one meaning the UK would participate in European elections 10 Downing Street/AFP/Getty Brexit so far: in pictures European Council summit Theresa May’s request to extend triggering Article 50 until the end of June was rejected by the EU, and instead offered a shorter time frame. She accepted the offer of a delay until May 22 if her withdrawal deal is approved by Parliament. If MPs rejected it for a third time, the EU said Britain must propose a new plan by April 12. Ms May said she will not support a long delay because it would mean Britain participating in elections for the European Parliament Getty Brexit so far: in pictures Brussels confirms preparations for a no-deal Brexit are completed They warned that it is “increasingly likely” the UK will crash out. In a statement the European Commission (EC) said “preparedness and contingency work”, which the EC has been conducting since December 2017, was now finished. The announcement came days after EU leaders agreed to a request by Theresa May to extend the UK’s Brexit date AFP Brexit so far: in pictures May resigns British Prime Minister Theresa May reacts as she delivers a statement in London, Britain, May 24, 2019. REUTERS/Simon Dawson SIMON DAWSON Reuters

“In that context President Tusk will propose an additional, extraordinary European Council in November that will be discussed in Salzburg.”

Brexit is however somewhat taking a back seat at the Salzburg summit, with migration and security set to be the headline issues dominating the agenda.