Liverpool have spent heavily this year as they attempt to close the gap on champions Manchester City, splashing out more than 200 million pounds for Alisson, Naby Keita, Fabinho, Xherdan Shaqiri and Virgil van Dijk.
And Klopp laughed off Mourinho's comments, stating that moves in the transfer market do not necessarily guarantee success.
"But I heard as well that Jose found me amusing and one of my biggest goals in life is to make José smile!"
"The problem is you have to invest well and honestly I think they did very well because every player they bought are quality players and I'm happy for them. I would never talk about Manchester United if no-one asked me about it", he said.
"And I'm also happy to smile and to see that, you know, you can change your opinion and change as a person".
"If there's competition in training then the training is intense, and then you have the pressure of a weekend that if you don't put in good performances then your place is maybe up for grabs".
"What can I say about that? Jose can say what he wants to say to be honest", Klopp said in response on Friday. We don't need 54 players and 20 goalkeepers.
Liverpool play Manchester United on Saturday in their last International Champions Cup friendly before hosting West Ham United at Anfield in the Premier League on 12 August.
Klopp's response follows Mourinho's suggestion Liverpool will have set a "Premier League record" this season, after spending almost £250m in the last 12 months.
"It's pre-season, but it's United against Liverpool, so big game".
"The first part of the season was crucial, and they were too far away from us from quite early on really". Especially when it's America, I can imagine people like it.
Now, the source adds that United have specifically told him that he isn't for sale, and that a crucial role awaits him at the start of next campaign, despite his subdued role in the final weeks of last season - a flaw which was a mixture of injury and Mourinho trying new things out.