Granit Xhaka was sent off for Arsenal at Anfield after less than half an hour, but a Liverpool team without top scorer Mohamed Salah, Sadio Mane or Naby Keita were unable to take full advantage.
And the Reds boss has called on the players to respond at the Emirates next Thursday when they are entertained by the Gunners with a place in the final up for grabs against Chelsea.
A disappointing performance saw the Reds register just one shot on target – in the 92nd minute – and Klopp concedes that his team fell well short against a disciplined Arsenal.
“Our situation, we said it before, it’s not an excuse, it’s an explanation for obvious reasons, we had to change the lineup tonight,” Klopp said.
“I really like how we started the game, I really liked what I saw in the beginning. We were on the front foot, we switched it at the right moments.
“We started the game like we wanted to start. Then it was a red card and playing against the low block was difficult.
“On top of that we made a few wrong decisions. It looked like we felt under pressure, which didn’t make sense.
“It is a typical situation: you go for the win but you can also lose something.
“That’s what I saw in the first half. We tried to change things in the second half with the way we had to defend us.
“Curtis Jones tried to give them some different problems.
“I thought the boys did quite well when we tried to do the same thing on the right side but we couldn’t create enough for the situation we were in for playing against 10 men for I don’t know how long.
“This is a cup competition, it is a two-legged semi-final and it is half-time and 0-0 and even when Arsenal feel in a better situation we don’t think this tie is over for us.
“We will give it a proper go next Thursday.”
Klopp added: “It looked like we were under pressure. That makes no sense but that is human.
“You go out there to win. It’s difficult against a well-drilled formation.
“We didn’t create enough, we didn’t do lots of things not good enough. But in the end it’s 0-0, half time, let’s go.
“I know we can play better, we know we have to play better.
“A lot of things I liked, but the general outcome was not good enough.
“That’s the truth of this game and we have to accept it.”