Ukraine's bid to join the European Union (EU) is "within reach" but requires "hard work, determination and above all unity of purpose," European Commission President Ursula von der Leyen said.
Addressing the Ukrainian parliament through a video link, she added on Friday that the path towards EU membership required reforms in many areas, including tackling corruption. She also took note of the steps Ukraine had already taken in this direction.
"You have created an impressive anti-corruption machine. But now these institutions need teeth, and the right people in senior posts," she said.
Von der Leyen added that Ukraine should appoint new heads for the Specialised Anti-Corruption Prosecutor's Office and National Anti-Corruption Bureau as soon as possible, Xinhua news agency reported.
She also highlighted the need to reform Ukraine's constitutional court, which requires legislation outlining selection procedures for judges in line with the recommendations of the Venice Commission.
"Many of the laws and institutions you need are already in place. Now is the time to translate rules and bodies into positive and enduring change," she said.
Von der Leyen was addressing the Ukrainian parliament following the approval of Ukraine and Moldova as candidates for EU membership on June 23.
Ukraine applied for EU membership shortly after the conflict with Russia had begun at the end of February. The country handed over its application on February 28, while Moldova applied for EU membership on March 3.