Klopp commented on the longtime rivals during an appearance on the freekickerz YouTube channel. Messi and Ronaldo are regarded as two of the best soccer players in history. They have won 11 of the past 12 Ballon d'Or awards, the most prestigious individual honor for soccer players in the world.
"For me Messi [is better], but I couldn't admire Ronaldo more than I do already," said Klopp, who also called both players "almost impossible to defend."
Ronaldo has 725 goals and 220 assists in 1,000 games. Messi has 697 goals and 289 assists in 856 appearances.
"Messi has much lower physical requirements from birth on," Klopp said of the 5-foot-7 Barcelona star. "If you could paint yourself a perfect player, it would have Ronaldo's height [6-foot-2], he could jump and run as high or quick as Ronaldo can do. And what is then even added to that is his total attitude, it is absolutely perfect and professional. It couldn't be any better.
"And on the other side there is the small Messi who makes everything look so simple. And therefore I like him maybe a little bit more as a player on the pitch. But Cristiano is also an absolutely incredible player."
Klopp also noted that some younger players have "similar potential" to Ronaldo and Messi.
Liverpool has a large lead over Manchester City in the Premier League standings, with the Reds in first place by 25 points. The Premier League season was suspended in April but the United Kingdom announced Monday that the league can restart with no spectators present as early as June 1.
Ronaldo and Messi were more intense rivals when Ronaldo played for Real Madrid in La Liga before he joined Juventus in Serie A. The Italian league has been suspended since March but players were allowed to resume training Monday. La Liga players have also returned to train.
Barcelona has a slight lead on Real Madrid for first place in La Liga. Juventus has a one-point lead on Lazio at the top of Serie A.