Jurgen Klopp has admitted that Liverpool must "suffer" at the hands of Barcelona if they are to stop Lionel Messi from carrying out his "threat" to bring the Champions League trophy back to the Camp Nou.

Liverpool, last season's beaten finalists, face the Spanish champions in Wednesday's semifinal first-leg after cruising past Porto in the previous round to book a place in the last four.

But after destroying Manchester United in the quarterfinals with a virtuoso performance in the home leg a fortnight ago, Messi goes into the clash with Liverpool closing in on fulfilling the promise he made to the Barca fans at the start of the season.

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"Last season was really good as we did the double, but we all felt bad about how it went in the Champions League," Messi said in September. "We promise that this season we will do all we can to bring that beautiful trophy back to the Camp Nou."

And although he goes into the game having failed to manage a team to victory against a Spanish club in Spain, Klopp insists that Liverpool can overcome Barcelona and Messi despite the Argentine forward's own determination to lead Barca to glory.

"Messi said at the start of the season that they wanted to bring back this cup," Klopp said. "That sounded already like a threat to me!

"But now we are here, we want to go to the final as well.

"We won't be perfect tomorrow, we will make mistakes, we will suffer, 100 percent. It will be so difficult, but I couldn't be more excited to play and I hope I can transport my players so they feel the same.

"It is not only about Messi, but it is about Messi of course. Can we concentrate on Messi? We should, in certain moments, but then they have 10 world-class players around who can decide the game.

"They have the highest quality team, they are already Spanish champions.

"But we saw the game against Real Sociedad and [Sociedad] did really well. Levante did really well a couple of days ago.

"Barcelona, the better the opponent, the better the competition, the higher the stakes, the more they are in. They are champions of Spain, so now they can focus completely on the Champions League. We are really looking forward to it, but it will be tough."

With Liverpool hosting the second leg at Anfield next Tuesday, Klopp admits the priority is to keep the tie alive for the return fixture.

"I would say that a draw is not the worst result in the world," he said. "Not that we will go for it, but it would be OK.

"So many people came to Barcelona and had an idea on how to play, and in the end they got a proper knock, so we know how tough it will be.

"But two years ago it was a big, big thing for the club to qualify for the Champions League. Now for the second time in a row we are here in the semifinal, that's big.

"It's only positive and everybody sees it like that. We don't need a guarantee.

"But we want to stay in this competition, to get a result tomorrow that gives us a good chance to do it at home. Whatever that result is, we want it."

Liverpool, meanwhile, travelled to Spain with striker Roberto Firmino in the squad after the Brazilian missed last Friday's 5-0 win against Huddersfield with a muscle injury.

"If Bobby is 100 percent ready, then he will maybe play," Klopp said. "He's here, he trained today, we have another session tomorrow. Then I have a decision to make."