BRUSSELS (Reuters) - European Union leaders are likely to hold a special summit on Brexit in mid-November when they hope to be able to sign off on a divorce deal with Britain, diplomats and officials said on Monday.

Anti-Brexit demonstrators wave flags outside the Houses of Parliament, in London, Britain, September 10, 2018. REUTERS/Hannah McKay

With the Irish border issue still the main stumbling block, EU ministers meeting in Brussels next Tuesday will discuss holding the extraordinary summit because they no longer expect to clinch a deal at a regular gathering scheduled for Oct.18-19.

Earlier, the EU’s Brexit negotiator Michel Barnier told a forum in Slovenia he believed a divorce deal with Britain could be agreed in six to eight weeks if negotiators are realistic in their demands.

Barnier’s comments pushed sterling to a five-week high.

Some diplomats said Nov. 13 was one date under consideration for the extraordinary summit, though others said it was still a moving target.

Some EU officials say a deal with Britain in December, or even as late as January, could leave just about enough time for the British and the European parliaments to ratify the agreement.

The least likely scenario, but one that some EU diplomats have also considered, is that Britain would ask to prolong the talks beyond the current exit date of March 29, 2019.

Such an extension would be domestically very complicated for British Prime Minister Theresa May, who is under heavy pressure from sections of her Conservative Party to honor that leaving date. The other 27 EU member states would also have to agree unanimously to any extension of the negotiations.

EU sources say that would only be possible if the negotiators were really very close to sealing a deal and ran out of time for purely technical reasons, rather than because of political wrangling.

In any case, they say an extension would only be possible for a few weeks as the current EU parliament - which must sign off on any Brexit deal - holds its last plenary session on April 15-18, 2019.

The EU will hold elections in May to pick a new assembly and the consensus in Brussels is that Britain must be out by then.