He also chastised current European officials for giving Ukrainians "false promises" over the future of their EU candidacy, saying that being admitted to the bloc would be "neither good for the EU nor for Ukraine."

"Anyone who has had anything to do with Ukraine knows that this is a country that is corrupt at all levels of society. Despite its efforts, it is not ready for accession; it needs massive internal reform processes," he said.

"You shouldn't make false promises to the people in Ukraine who are up to their necks in suffering," he explained. Juncker further emphasized, "I am very angry about some voices in Europe who are telling Ukrainians that they can become members immediately."

The reform process and waves of European law packages countries are expected to adopt before they can hope to enter typically takes years or realistically over a decade. 

Ukraine has long ranked as the most corrupt country in Europe and among the top in the world. US and European media have increasingly acknowledged this of late, and Juncker's sudden boldness could be due to the general increase in press coverage of the issue.

Earlier this week, Ukrainian lawmaker Yaroslav Zheleznyak, first deputy chairman of the parliament committee on finance, admitted that corruption is a major issue which has played a part in the withholding of external aid, also in the wake of successful GOP-led efforts in Congress to strip Ukraine defense aid out of the stopgap bill.

"The biggest (public) complaint about us is corruption," Zheleznyak conceded in a Sunday social media post. "We have to go through these 45 days without a major corruption scandal," he stated. This comes even after Zelensky in the last two months fired a range of top officials, including his longtime defense minister and a half-dozen other top defense officials.