He revealed that centre-back Virgil van Dijk is "100% available" having been absent for the second of the Netherlands' recent Euro 2020 qualifiers.
For Mohamed Salah, Andy Robertson and Joel Matip, Klopp said he "cannot say 100%," adding: "Today [Friday] is a very important session to judge that, especially with the players who came back late."
Turning his attention to the rest of the squad, Klopp was equally noncommital, saying:
"Fabinho and Bobby [Firmino] and Ali [Alisson] played on Tuesday [for Brazil]. Gini Wijnaldum played on Tuesday [for the Netherlands], so we have these players where we really need to have a look at how they react and what makes sense for them or not.
"It’s always how it is with the first game after the international [break]. We have to wait until the last second pretty much to make the decision."
Xherdan Shaqiri trained all week as he recovers from a calf injury, but Klopp said there is "no reason to rush."