European Commission head Jean-Claude Juncker is first expected to rally the troops on Wednesday in his annual State of the Union address, restating his conviction that Europe alone can provide the answers.
European Union leaders, 27 without Britain, then meet in the Slovak capital Bratislava on Friday to plot a new course with security concerns top of the agenda, according to EU council president Donald Tusk.
"The union and its member states must demonstrate our strong determination and ability to address the major concerns and worries of its citizens," he said.
"For me it is clear that our first priority must be to secure our external borders," he added.
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Britain's shock June 23 vote to leave the EU has plunged the bloc into crisis.
The EU has been on the defensive since the 2008 global financial crash threw millions out of work and tough austerity policies undercut its key claim that it alone can guarantee a better economic future for its 500 million citizens.
Adding to the sense of chaos, deadly Islamic State group claimed attacks in France and Belgium left people asking how the jihadis could strike at the very heart of Europe with such apparent ease.
Against this backdrop, there can be "no taboos" in discussing the EU's future, Tusk said, adding: "Bratislava needs to show that the political elites in Europe are not detached from reality."
Brexit itself is however off the summit menu, with EU leaders first waiting for British Prime Minister Theresa May to say what she wants out of the new relationship.
Meanwhile Juncker, under pressure amid reports about his health, will use Wednesday's speech to push a "positive message" for the EU, with plans for more investment and for boosting cooperation with African countries to stem migration.
Janis A Emmanouilidis, Director of Studies at the European Policy Centre (EPC) in Brussels said the EU wanted "to show its citizens in concrete terms that it is still able to work together.