The Reds take on the Spanish giants at the Camp Nou as they look to bring back a positive result to Anfield for the second-leg next week.
There were concerns over the fitness of Roberto Firmino after he missed Liverpool's 5-0 victory over Huddersfield on Friday night, however the Brazilian has overcome a muscle strain to travel with the rest of the squad.
Firmino returned to training on Tuesday morning after missing two sessions and Klopp sounded hopeful of his striker's inclusion in the match-day squad.
"Yes, of course [it's a huge boost]," Klopp said. "We all knew from the beginning it would be a race. We don't have to make a decision today because there's no game today, we can wait.
"It looked good so far but until tomorrow I have to make that decision – after lunchtime tomorrow. That's what I will do."
The entire squad was involved in training barring Adam Lallana. Brazilian midfielder Fabinho, who also missed the last fixture due to concussion he suffered against Cardiff, was involved in training and is in contention to start.
There is also a return for Alex Oxlade-Chamberlain to Liverpool's travelling Champions League squad after he came through unscathed from a 20-minute cameo against Huddersfield on Friday night.
The squad arrives in Spain this afternoon with Klopp holding a press conference from the Camp Nou at 7pm BST.
Liverpool full 23-man squad: Fabinho, Van Dijk, Wijnaldum, Lovren, Milner, Keita, Firmino, Mane, Salah, Gomez, Alisson, Henderson, Sturridge, Moreno, Oxlade-Chamberlain, Mignolet, Shaqiri, Brewster, Robertson, Origi, Matip, Kelleher, Alexander-Arnold.