The EU's new foreign affairs chief Federica Mogherini is in Turkey to urge the government there to step up its fight against Islamist fighters in Syria and Iraq.
Mogherini will meet with Turkey's President Recep Tayyip Erdogan today to encourage him to implement stricter border controls, with a view to stemming the flow of international fighters joining the Islamic State.
Accompanied by senior EU officials, Mogherini will also discuss Turkish accession to the EU, which has fallen down the agenda over the past decade.
The EU Commissioner for Enlargement Johannes Hahn, who will be on the trip, said: "We are committed to moving forward EU-Turkey relations and keeping the accession negotiations on track. However, further reforms are needed to provide solid ground for progress. To achieve this, we need to have an even closer and deeper relationship with Turkey."
With Russia hoping to step up its relationship with Erdogan in coming months with a view to finding an alternative route for the South Stream Pipeline, Mogherini will try to convince the Turkish premier to back western sanctions on Moscow.
The EU vetoed Russia's plans to build the pipeline through Bulgaria, adding to speculation that Turkey would be approached to host it.
Mogherini said in a statement: "The visit to Turkey next week, together with Commissioners Hahn and Stylianides is a strong indication of the strategic importance of the EU-Turkey relationship and our desire to step up engagement in view of shared interests and common challenges."
The infographic below details the levels of foreign fighters who have travelled to Iraq and Syria to join ISIS.