The Austrian has also outlined that Norris is on the reigning champion’s radar, disclosing that Red Bull previously had an agreement with the Briton until options in his McLaren deal saw him stay put with the British side.
“Perez is not consistent [enough]; he is not always focused,” Marko told Austrian television station ServusTV.
“Perez has a contract until 2024, and Norris has a contract until 2025. Unfortunately, it’s that long.
“He [Norris] is definitely a candidate for us. At Toro Rosso, we had already reached an agreement with him at the time until his manager realised there was an option for a McLaren contract.
“In terms of youth and speed, he would suit us very well. Sergio, on the other hand, is already over 30 and is expecting his fourth child.
“So he also has other interests, so you have to see what happens next.”
Norris has previously disclosed that talks took place with Red Bull before he agreed to renew his contract with McLaren early last year, which runs until the end of 2025.
The 23-year-old publicised last Thursday at Monza that he and Verstappen have regularly talked about becoming team-mates in the future, something Norris would be open to.
When asked on Friday ahead of the Italian Grand Prix whether the team would consider another approach for Norris, Red Bull Team Principal Christian Horner said: “Look, Lando is a great driver, there’s no doubt about that, and you can see his potential is growing.
“But he’s a McLaren driver, you have to respect the agreements that are in place.
“But he’s one of a few drivers at the moment that… He’s doing a great job in the sport and, of course, we have our drivers confirmed for ’24. In ’25 we have one seat open and as you can imagine, there’s not a shortage of interest in that seat but it’s a long way away at the moment.”