Apart from meeting Tusk and Juncker, Šarec is to hold a number of bilateral meetings. As for Slovenia's migration policy in the future, he has said that the country will continue advocating solidarity among member states under clear and fair rules.

He also said in an interview for TV Slovenija on Friday that Slovenia had always been a constructive EU member "and the solo actions of the Visegrad group aren't our kind of thing ... Our foreign policy must be coordinated and stable."

The summit will start with a working dinner dedicated to migration issues. The host, Austrian Prime Minister Sebastian Kurz, will brief heads of state about his and Tusk's recent visit to Egypt with which the EU wants to cooperate more closely on migration issues.

Tonight, UK Prime Minister Theresa May will present her view of the progress in Brexit talks, while heads of state will be able to exchange views on the topic with the bloc's chief negotiator Michel Barnier on Thursday.

Kurz has recently said that good preparations for Brexit were the most important challenge of Austria's EU presidency. Meanwhile, Tusk has said in the invitation to the event that the summit must go over the progress made in Brexit talks so far and plans for the future.

The summit will also discuss internal safety, above all cooperation among police forces and justice systems, as well as stricter border controls and internet safety.

This will be the first summit after the European Parliament launched a procedure to impose sanctions against Hungary due to policies of its Prime Minister Viktor Orban.

The summit will be preceded by a meeting of national party leaders from the ranks of the European People's Party (EPP), which may also discuss a potential exclusion of Orban's Fidesz.