European Commission President Ursula von der Leyen arrived in Kiev on Tuesday for talks with Ukrainian President Volodymyr Zelensky.
Von der Leyen said the EU's focus was to increase pressure on Russia, ensure full implementation of sanctions and close existing loopholes.
"The focus now is on tight implementation of the sanctions and taking action to avoid circumvention. We are determined to close existing loopholes. No-one should doubt that," the EU leader told a pool reporter for the European Newsroom.
Her trip takes place on a symbolic day, as the European Union celebrates on May 9 the lasting peace between its members that followed the end of World War II in 1945, while Russia marks its victory over Nazi Germany with an annual military parade.
On Monday, Zelensky announce that Ukraine would start commemorating the date, known as Europe Day.
Von der Leyen noted the significance of the date. She called her presence on this date "symbolic" but also a "sign of a crucial and very practical reality: the EU is working hand in hand with Ukraine on many issues."
Ukraine was named an official candidate country for EU membership last year and is awaiting an assessment by the commission on whether its reform efforts were sufficient to start formal accession talks.
Von der Leyen did not offer any hints as to when Ukraine might make it into the current 27-member union but did say that "Ukraine is part of our European family."
The talks with Zelensky were also for "preparing the ground for the start of accession negotiations," she said.
The two leaders will discuss issues ranging from arms deliveries to substantial EU financial support for Ukraine to ensuring that Russia is held accountable "for its crime of aggression," she said.
“We are continuing to increase pressure on Russia," she added.
Brussels has provided military, financial and humanitarian support to Kiev worth €67 billion ($75 billion) so far, with work being under way on a new set of economic sanctions on Russia.
The bloc is planning to further restrict its exports, according to EU sources, in a bid to tackle the circumvention of the existing sanctions on Russia by exporting goods via other countries which do not have punitive trade measures on Moscow in place.
Von der Leyen last visited Kiev in February together with European Council President Charles Michel. At the time they promised Ukraine their support on its way to EU membership, but did not set a timeline.
- EC President