The Serb has been superb with Hertha this season, drawing comparisons with former Germany captain Steffen Effenberg.
"Marko is an example of players with quality that we normally cannot afford. But we can get him on loan in one or two seasons. And in the future he will really be an asset to Liverpool," said Preetz, quoted by Goal.
"The question is when Jürgen Klopp sees him at that level. He already helps us, so we would like to keep him. But that decision is only made after the season."