Britain was excluded from European Union summit talks for the first time in more than 40 years on Wednesday as the bloc's other 27 members discussed how to react to London's shock decision to exit the EU.
British voters decided to leave the EU in a June 23 referendum. With that vote, the 28-member EU is poised to lose a country that boasts one of the world's top five economies, United Nations veto powers, nuclear capabilities, a strong army and a world-class financial industry.
"The outcome of the [British] referendum creates a new situation for the European Union," leaders said in a statement. "We are determined to remain united and [...] stand ready to tackle any difficulty that may arise from the current situation."
"Nothing should keep Europe from advancing," French President Francois Hollande declared.
Leaders met on Wednesday in an unusual 27-member format that, in a sign of things to come, excluded Britain, a member of the bloc since 1973.
Prime Minister David Cameron bid farewell to his EU peers on Tuesday, after a meeting he described as dominated by "sadness and regret."
The EU 27 renewed calls on Britain to activate "as quickly as possible" proceedings to leave the bloc, spelling out that "there can be no negotiations of any kind before this notification has taken place."
Turning to internal affairs, the leaders acknowledged that "many people express dissatisfaction with the current state" of the EU and said they had launched "a political reflection to give an impulse to further reforms."
German Chancellor Angela Merkel explained that this would not entail any rewriting of EU rules. "These treaties are a very, very good foundation," she said. "We would really be doing the wrong thing if we start a treaty discussion again."
Providing more "security, jobs and growth" were listed as priorities in the leaders' statement, but no concrete initiatives were agreed. More summit talks among the 27 were scheduled to take place on September 16 in Bratislava, Slovakia.
EU President Donald Tusk said migration had to be brought under control, noting it was "absolutely clear that irregular migration was and is one of the most important reasons for this crisis of self-confidence in Europe."
In the run-up to the summit, a Franco-German paper laid out a broader reform agenda, including an expansion of EU military and anti-terrorism capabilities and the creation of a eurozone fund by 2018 to support economies in crisis.
France and Germany, the EU's leading powers, said in their paper that progress should be possible even if not all member states are on board - a view shared by Belgian Prime Minister Charles Michel as he spoke in Brussels.
Countries that want to integrate more quickly should "be able to do so without being hindered by those who choose to take a bit more time to advance," Michel said. Countries in Central and Eastern Europe are suspicious of such moves towards a "two-speed" Europe.
In addition to negotiating with Britain and bringing their houses in order, EU leaders might also have to contend with demands from Scotland. After its voters rejected Brexit, Scotland is considering moves to split from Britain and remain an EU member.
Scottish First Minister Nicola Sturgeon was visiting Brussels on Wednesday for initial talks with European Parliament President Martin Schulz and Commission President Jean-Claude Juncker aimed at protecting Scotland's place in the EU.
"I will listen carefully to what the First Minister will tell me but we don't have the intention [...] to interfere in the British process," Juncker told reporters. "It is not our duty and not our job," he added.