The Brazilian forward, 27, missed the Premier League win over Huddersfieldon Friday with a muscle tear.
"If Bobby is 100% ready to play, then he will maybe play," said Klopp.
"He's here. He trained today. Tomorrow we have another session and maybe I have to make a decision."
Midfielder Fabinho is available again after sustaining a head injury at Cardiff on 21 April.
Both players were included in the 23-man squad for the Nou Camp showdown (20:00 BST).
Klopp added that Firmino's recovery "looks good so far" and he has until lunchtime on Wednesday to prove his fitness.
"We all knew from the beginning it would be a race," said the Anfield boss, whose team are vying with Manchester City for the Premier League title.
"We don't have to make a decision today because there's no game today, we can wait.
"I have to make that decision after lunchtime tomorrow."
Barcelona sealed their 26th La Liga title with a 1-0 win over Levante on Saturday.
Messi-inspired Barca target first final since 2015
Ivan Rakitic says captain Lionel Messi's desire to win the Champions League is proving an inspiration for Barcelona.
Argentine forward Messi stood on the pitch at the start of the season and told supporters he would help to bring "that beautiful cup back to Nou Camp" after three consecutive years of quarter-final defeats.
And Rakitic says the players follow "whenever our captain says something".
"Leo has been a La Liga champion 10 times in 15 years and, of course, after seeing him lift the cup [La Liga's trophy on Saturday] with such happiness, that motivates everyone," said the Croatian midfielder.
"If Leo is happy to win every title, it makes us even more eager too. We know we're Barca, we have to give everything and following the best player in history gives us more confidence to do that."
Barcelona manager Ernesto Valverde says Liverpool are a "powerful team" and his side must play "two good matches" to qualify for their first final since 2015.
"Liverpool play with a great level of pressure and rhythm. They'll be a very difficult opponent to beat," said Valverde.
"Our intention is to win, but we know the value of stopping them from scoring."