EU leaders will try to reboot the struggling bloc this week, focusing on security and defence to provide a new sense of purpose after the Brexit vote revealed deep fears over globalisation, terrorism and migration. 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. "I have no doubt that the three main challenges are uncontrolled irregular migration, terrorism and the fears of globalisation," Tusk said in Stockholm Friday as part of a tour of European capitals before the summit. "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. 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. A newly assertive Russia took advantage in Ukraine while turmoil in the Middle East and North Africa sent migrants flooding into southern Europe, straining the bloc's much vaunted solidarity to the limit. 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. Defence will also be a key theme with France and Germany expected to push a plan to enhance cooperation across the bloc, while falling short of the "EU army" that some eastern states have called for. 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."