European Commission President Ursula von der Leyen has said there will be no shortcuts to joining the European Union.
Her comments come at the annual Globsec summit in Bratislava where leaders discuss sustainability and security across the European continent.
Following Russia's invasion of Ukraine, EU member states are debating Kyiv's demand to fast-track its application to join the bloc.
"Our standards and conditions in an EU accession process must be met," said von der Leyen.
"There is neither a wildcard nor short card, but how fast, how quickly, how the speed of such a process is - this is depending on the country itself and our support."
Ukraine's President Volodymyr Zelenskyy also joined the meeting via a video link.
He called for the west to put more pressure on Russia and thanked world leaders for their economic and military support.
The Ukrainian president also addressed Luxembourg's parliament on Thursday morning - on the 99th day since Moscow's assault on the war-torn country began.
He said almost 20% of the country is now controlled by Russia - an area spanning 125,000 kilometres.
Almost 300,000 square metres are scattered with unexploded mines and ammunition.