BRUSSELS (Reuters) - EU and UK negotiators on Friday talked up prospects of agreeing a Brexit deal this autumn, citing recent progress in detailing very close security cooperation to take effect after Britain leaves the bloc.

The European Union’s Michel Barnier said it was “possible” to get an agreement in time for a summit of all the bloc’s leaders in Brussels on Oct. 18-19, though a delay into November was also possible.

After his latest talks with Barnier, Britain’s Brexit minister Dominic Raab said he was “stubbornly optimistic” and “as confident as before, if not more” that there would be a deal.

The two said they made progress over security cooperation, including on exchanging data.

“Europe’s security is the United Kingdom’s security,” Raab told a joint news conference.

Barnier said unresolved issues included geographical indication labels for specialised local products, nuclear cooperation, data protection and the role of the EU’s top court in policing the agreement.

After weeks of warning of growing risk of a damaging no-deal Brexit and signalling delay was expected if there is to be any Brexit deal, the EU’s strategy is now to highlight how close cooperation with Britain is possible after Brexit to make London more willing to accept divorce terms.

That goes specifically for the sensitive issue of the EU-UK land border between Ireland and British-ruled Northern Ireland, where the EU wants a “backstop” solution in case of no deal, which includes terms that are anathema to London.

“We must have a detailed backstop solution, which is legally operational in the withdrawal agreement,” Barnier said. “This backstop is critical, it’s essential to concluding these negotiations. With no backstop, there will be no agreement.”

Barnier said the EU and UK were working for an “unprecedented partnership” in the future that would include a broad free-trade agreement, as well as sectoral cooperation deals in aviation, security and research, among others.

“It’s unprecedented, such a partnership with a third country,” Barnier said. “But the preliminary condition to that is that we have to organise an orderly withdrawal of the UK. That’s the condition of the unprecedented partnership in the future.”