SOFIA (Reuters) - The EU’s chief executive on Thursday told the six Western Balkan countries that future membership of the bloc was theirs to secure, but toughened a message that reforms were more important than timelines.

European Commission President Jean-Claude Juncker speaks following a meeting with Bulgarian and Western Balkan leaders in Sofia, Bulgaria, March 1, 2018. REUTERS/Stoyan Nenov

Wrapping up his first tour of the region as Commission president, Jean-Claude Juncker sought to show Serbia, Montenegro, Macedonia, Albania, Kosovo and Bosnia that the bloc was serious about integrating them, starting from 2025.

“Accession is not a dream but a reality, a reality that is going to come,” Juncker told reporters in Sofia after joining the region’s heads of state for a final meeting that followed a trip through each country.

EU leaders will endorse the EU’s 2025 goal, potentially the accession date for Serbia and Montenegro, at a Western Balkans summit in May in Sofia.

“But more importance needs to be paid to the substance than the calendar,” Juncker said, touching on wider concerns.

Some EU governments are wary of letting in countries still scarred by wars fought along ethnic lines in the 1990s and dogged by a reputation for lawlessness.

They are also anxious not to repeat what they believe was the rushed accession of Romania and Bulgaria in 2007 and the poorly managed migration of eastern European workers to Britain that turned many Britons against the EU.

Still, Brussels wants to reclaim the Western Balkans as its own.

Concerns about Russia’s assertiveness on its borders have grown since its annexation of Ukraine’s Crimea region in 2014, and were exacerbated in the Balkans after Montenegro accused Moscow of supporting a failed coup in 2016.

Meanwhile, Chinese investment in the region, though welcomed by governments, is seen as undermining standards because it does not come with the same stringent requirements as EU aid.

Echoing earlier comments, Juncker said the candidates must root out graft and organized crime and end all bilateral territorial conflicts before they can accede to the bloc.

The European Bank for Reconstruction and Development has said that if the Western Balkan countries did not speed up reforms, it could take them many generations to catch up with living standards of EU states.

Albania and Montenegro are already members of NATO while Macedonia is likely to be offered the chance to join the U.S-led alliance, often seen as a springboard to EU membership, if it can overcome a dispute over its name with Greece.

Underlining the renewed focus on the region, Juncker said: “I will be returning to Brussels with the conviction, which I already have in fact, that the place of the Western Balkans is at the heart of the European Union.”