Ukraine's bid to become a candidate to join the EU will get a clear signal next week, the bloc's chief Ursula von der Leyen said Saturday on a surprise visit to Kyiv.

Von der Leyen said talks she held with Ukrainian President Volodymyr Zelensky "will enable us to finalise our assessment by the end of next week".

It was the first time the EU has publicly given timing on when the commission will deliver its opinion. The bloc's 27 member countries need to decide whether to allow Ukraine to start accession negotiations.

Shortly after Russian's February invasion, Zelensky started pushing for Ukraine's rapid admission into the European Union and has demanded an answer on its candidacy before the end of this month.

But officials and leaders in the bloc caution that, even with candidacy status, actual EU membership could take years or even decades.

Ukraine sees the prospect of joining the EU as a way of reducing its geopolitical vulnerability, which has been exposed by Russia's war inside its borders.

Von der Leyen, appearing alongside Zelensky for a brief declaration to media, did not hold out any promises.

"You have done a lot in strengthening the rule of law, but there still need to be reforms implemented, to fight corruption for example or to modernise this well-functioning administration, to help attract investors," she noted.

Instead she focused more on the future reconstruction of Ukraine, once the war has ended.

That, von der Leyen said, "should be a process that is fully owned by Ukraine", with the EU standing by to help and to contribute to a roadmap "to support Ukraine in pursuing its European path".

There are expectations that Ukraine's EU candidacy status will be green lit at an EU leaders' summit taking place on June 23-24 -- though with stern conditions attached.

This was EU chief Ursula von der Leyen's second visit to Kyiv since the start of the war
This was EU chief Ursula von der Leyen's second visit to Kyiv since the start of the war AFP / Sergei SUPINSKY

Several EU countries, including Sweden, Denmark and the Netherlands, are reluctant to give their nod and Germany has not set out its position.

Some have concerns with Ukraine's problem with corruption documented before the war, and the fact that other countries such as North Macedonia and Albania are already further along the EU candidacy path.

EU officials will pore over Ukraine's bid next week, with von der Leyen and her commissioners getting together on Friday to unveil their opinion ahead of the summit a week later.

Von der Leyen's trip to Kyiv was her second since the Russian invasion in late February.

Her last one, on April 8, was to hand Zelensky a questionnaire his officials needed to fill to provide details that would help inform the European Commission's opinion it has to give to the European Council, representing the EU's member states.

On that April visit, von der Leyen said "Ukraine belongs to the European family".

The European Union is helping channel weapons to Ukraine through a two-billion-euro ($2.1-billion) fund and has given it more than 700 million euros in aid and in-kind assistance since the invasion.

EU countries are hosting nearly five million Ukrainian refugees who have fled the war.