LUXEMBOURG  - British Prime Minister Boris Johnson’s spokesman says the U.K. wants to nail down a Brexit deal “as soon as possible and we want to make progress ahead of the EU council (summit) on Thursday.”

Spokesman James Slack said Tuesday: “We are working hard. The prime minister is aware of the time constraints that we are under.” EU leaders are to meet Thursday and Friday in Brussels with Brexit topping the agenda as an Oct. 31 deadline looms for Britain to leave the bloc. Slack says Johnson discussed progress in Brexit negotiations during a “constructive” phone call Tuesday morning with French President Emmanuel Macron.

Slack says Johnson told Macron that “in advance of the EU council (summit), U.K. officials would continue to work hard on securing a deal.” The negotiations are mainly focused on solving questions around the Irish border. A French diplomatic official says France hopes that a divorce deal with Britain will be negotiated by Tuesday night.

The official acknowledged a “positive momentum” on Tuesday after a phone call between French President Emmanuel Macron and British Prime Minister Boris Johnson.

He said a divorce deal with Britain is possible, but not guaranteed, as Brexit negotiators were still having talks on Tuesday.

He said the bloc’s members expect to have a clear idea later that day on whether a deal is on track or not. The official was speaking anonymously in line with the French presidency’s customary practices.

EU leaders are meeting for a two-day summit in Brussels from Thursday. Brexit will top the agenda as Britain’s Oct. 31 deadline to leave the bloc looms.

Irish Foreign Minister Simon Coveney says Brexit negotiators are facing a critical few hours to see if they can deliver a deal ahead of a summit of European Union leaders on Thursday. He said that from the EU side, the belief is that “this is difficult, but it is doable.”

He said the EU’s chief Brexit negotiator, Michel Barnier, noted to EU ministers that there had been “progress in the last number of days” but that there will need to be “significant progress today” to secure a deal in time. EU leaders begin their two-day summit on Thursday and want to avoid any negotiations about the precise details of any Brexit agreement. There has been talk that there could be another emergency EU leaders’ summit in the run-up to the Oct. 31 Brexit deadline.

Britain’s chief Brexit minister has made a last-minute trip to meet European Union colleagues and British Prime Minister Boris Johnson has postponed a Cabinet meeting — signs that talks on an EU divorce deal are reaching a critical point. Brexit Secretary Stephen Barclay flew Tuesday to Luxembourg, where EU ministers are meeting with the bloc’s chief Brexit negotiator, Michel Barnier. Barclay said as he arrived that talks needed “space to proceed.”

He said “detailed conversations are underway and a deal is still very possible.” Britain’s weekly Cabinet meeting has been moved from Tuesday to Wednesday, so Johnson can give ministers a better idea of progress.

Few details have emerged about the substance of talks, which center on keeping an open border between EU member Ireland and the U.K.’s Northern Ireland. Britain is scheduled to leave the EU on Oct. 31.  German Chancellor Angela Merkel is likening the effort to break the Brexit deadlock to “squaring the circle,” but is vowing to work until the last moment to secure an orderly British withdrawal from the European Union.

Merkel pointed to the difficulties of reconciling the U.K.’s desire to leave the EU customs union with the need to maintain an open border between Ireland and Northern Ireland.

In a speech to German machinery makers, she said that “what they are trying to negotiate is something like squaring the circle, and it is very, very complicated.”

She added that “we will work until the last minute for an orderly British withdrawal” but insisted that the EU is also prepared if no deal is reached.

Merkel said “one thing is clear already now.” Britain, she said, will develop into “another competitor on Europe’s doorstep and that will require the European Union even more strongly to be competitive and to take geopolitical responsibility.”