The Egyptian was stretchered off at St James’ Park due to a head knock sustained as he challenged Newcastle goalkeeper Martin Dubravka for a high ball.
“It’s a concussion so that means he would not even be allowed to play. So that’s it,” said Klopp at his pre-match press conference on Monday.
“He feels OK but it is not good enough from a medical point of view that is all. He’s desperate (to play) everything but we cannot do it.”
Klopp will also be without Brazilian striker Roberto Firmino due to a groin injury as his side face the huge challenge of trying to overturn a 3-0 first leg deficit to make the Champions League final for a second consecutive season.
“Two of the world’s best strikers are not available tomorrow night and we have to score four goals against Barcelona to go through after 90 minutes,” added Klopp.
“It doesn’t make life easier, but as long as we have 11 players on the pitch, we will try it.”
Luis Suarez’s first-half strike gave the Blaugrana an early lead.
The Reds came agonisingly close to getting a crucial away goal when Firmino’s strike was cleared off the line before Salah struck the post with his follow-up.