BRUSSELS (Reuters) - European Union leaders are likely to have to hold an emergency summit in November to consider any Brexit agreement struck with Britain, missing an informal deadline the previous month, diplomats in Brussels said.

European Union's chief Brexit negotiator, Michel Barnier attends a media briefing with Britain's Secretary of State for Exiting the European Union, Dominic Raab, after a meeting at the EU Commission headquarters in Brussels, Belgium August 21, 2018. REUTERS/Francois Lenoir

Agreeing the terms of Britain’s exit from the EU next March, as well as an outline of its future ties with the bloc, is proving a tall order. Delays have stirred talk that Britain could crash out of the EU with no agreements to replace nearly five decades of close cooperation in everything from food standards to space exploration and global diplomacy.

Negotiations on the divorce deal resumed after the summer break on Tuesday, but even the bloc’s Brexit negotiator signalled growing expectations that were increasingly unlikely to be wrapped up in time for a regular EU summit in October.

“I’m not going to say (it must come in) October. A few days here or there, beginning of November. But not much later than that, certainly,” Michel Barnier told a joint news conference with Britain’s Brexit minister, Dominic Raab.

Both men agreed that, while there has been progress in drafting possible cooperation between the EU and Britain on security and defence after Brexit, the Irish border and trade ties were still the key sticking points.

“If we have that ambition, that pragmatism and that energy on both sides, I’m confident we can reach that agreement by October,” Raab told the same news conference.

But some Brussels diplomats told Reuters the process could even slip into December, leaving little time for ratification of an agreement before Britain becomes the first country ever to leave the EU in March 2019.

“There is definitely going to be a real push for October and we’ll probably not be able to quite get there. So, while it has not formally been confirmed as yet, an extra summit in November looks most likely,” said a senior EU diplomat.

The Oct. 18-19 summit of all EU leaders has long been cast as the make-or-break moment for a Brexit deal, leaving enough time for the elaborate ratification process by EU member states and the European Parliament.

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But persistent disagreements, mostly over how to avoid border checks between the Irish Republic and the British province of Northern Ireland, have now cast that into doubt.

Gabriele Zimmer, a leftist German member of the European Parliament who deals with Brexit, doubts a deal can be reached by October. “It will be very hard,” she said.

“We didn’t see any concrete proposal that would work on the Irish border issue. November is the last moment. December is already too late for us.”

Another diplomat also said people and businesses affected by Brexit would have to wait longer for any clarity on a deal.

“Most probably not October. November is more likely,” the diplomat said. “December is really the very, very last call. If there is still nothing at the turn of the year, it’s hard to see businesses would not start implementing contingency plans.”

The sources stressed political infighting between pro- and anti-Brexit factions in Britain as a risk factor, pointing to the annual conference of Prime Minister Theresa May’s Conservative Party on Sept. 30-Oct. 3.

PRESSURE

Other milestones include a Sept. 19-20 informal gathering of EU leaders in Salzburg, Austria, where May is expected to make her case. The last regular leaders’ summit this year is scheduled for Dec. 13-14.

Asked whether it was still the British government’s aim to reach a deal in October, a spokeswoman for May said: “That is certainly what we are working towards, yes.”

London has fumed at a Brussels-proposed emergency plan under which Northern Ireland would effectively remain largely run by EU trade rules after Brexit, unless better ideas emerge.

The unity of the remaining 27 EU states in facing off with Britain has also started to show signs of wavering as the risk of a damaging “no-deal” Brexit rises.

Poland’s EU minister Konrad Szymanski told his peers in July the bloc may soon be forced to choose between Ireland and having any deal with Britain. This marked a departure from the EU’s mantra of standing by Ireland, where both sides fear a return to border checks could revive decades of sectarian violence.

But Warsaw has made clear that trade with Britain and mutual safeguards for citizens’ rights - more than three million EU nationals live in Britain, roughly half of them Poles - may be more important.

On its side, Britain is due to release this week a set of papers on potential effects of a “no-deal” Brexit.