The league has been halted since March 13 due to the COVID-19 pandemic but clubs can now train in small groups.
Klopp told Sky Sports television after a first session with 10 players on a sunny day at Melwood that he expected all his players to show up but they were under no pressure.
“It’s their choice so that’s clear,” said the German, who had two more training groups later on Wednesday.
“I said before the session ‘You are here on free will. Usually you sign a contract and then you have to be in when I tell you. In this case, if you don’t feel safe, you don’t have to be here’.
“There are no restrictions, no punishment, nothing. So it’s their own decision and we will respect that 100%.
“The boys are fine. We would never put anybody in danger to do what we want to do. Yes, we love football, and yes, it’s our job but it’s not more important than our lives or the lives of other people.”
Klopp said he felt “like a policeman, pretty much, wearing my uniform” as he set off for Melwood, with nobody allowed to shower or change at the ground.
Groups of five trained on separate pitches but Klopp said “it looked like football”.
The league will decide next week when to allow contact training as it seeks a June restart. Germany’s Bundesliga resumed matches last weekend.
Liverpool were 25 points clear of second-placed Manchester City and two wins from their first top-flight title since 1990 when the season was brought to a halt.