Premier League giants Liverpool thrashed Porto 4-1 on Wednesday to wrap up a 6-1 aggregate victory in their quarter-final.
Their reward is a showdown with Barcelona, who were inspired by Messi in a 4-0 aggregate win over Manchester United.
Klopp said Messi, who has scored 45 goals this season, had proven impossible to stop so far this campaign.
"Thank God I don't have to think about that and I have a few more nights," he told a news conference.
"Everybody tried it so far and nobody can do it, but we're looking forward to it.
"So many jobs to do before we meet Barcelona. We will see."
Last season's runners-up Liverpool were too good for Porto in the second leg thanks to goals from Sadio Mane, Mohamed Salah, Roberto Firmino and Virgil van Dijk.
Klopp is excited by the challenge of facing Barca, adding his team had made a "big statement" by reaching the semi-finals again.
"We play against Barcelona, I don't think too much about it but I'm really happy about the fact we play them," he said.
"We'll find things we think we could use but on the other hand, I don't care. We're in the semi-final, on Sunday we play against Cardiff [City], that's in my mind when I wake up tomorrow [Thursday].
"We can watch so many teams who tried it already, maybe we'll find something but I'm looking forward to it, just not tonight.
Mane— Liverpool FC (@LFC) April 17, 2019
"That's really good news and I'm happy for all the people in the club. Second year in the semi-finals is a big statement.
"We'll go there, everybody tries it. I'm really proud of the boys. We did it in different ways, that makes it even more special."