Liverpool and City are fighting it out at the top of the Premier League table, with just one point separating them with two matches remaining:
Mourinho, meanwhile, was sacked by Manchester United in December with the Red Devils 11 points off the top four after the club's worst-ever start to a Premier League season:
Talking on beIN Sports (h/t Dom Farrell of Goal) after Liverpool's 3-0 loss to Barcelona in the UEFA Champions League on Wednesday, Mourinho bemoaned the relative lack of backing he received at United compared to Klopp and Guardiola:
"I would love to go to a club and be in conditions to do what Jurgen and Pep did. If you look at the [Liverpool] team that started the game, how many of them were there when Jurgen arrived? A couple. And when Pep was not happy with the full-backs he had [at City in 2016-17] and in the [next] summer bought four [three] full-backs that he liked.
"When he bought one goalkeeper like Claudio Bravo and was not happy with Claudio Bravo, the next season he bought Ederson. When Jurgen is in the club and wins absolutely nothing for three-and-a-half years and he still has the trust, still has the confidence, still has the conditions to try to keep going and going.
"Probably this season they have a big chance to do it – the first time that they win a trophy. In my next job I will not be starting a conversation without knowing exactly what the club wants and what the club has to give in terms of structure and the club objectives."
Mourinho, 56, hardly had to work on a shoestring at United.
Paul Pogba was signed for £89 million, Romelu Lukaku for £75 million, Fred for £52 million, Nemanja Matic for £40 million, Victor Lindelof for £31 million and Eric Bailly for £30 million.
Guardiola took over City in the same summer as Mourinho joined United, and he has spent over £500 million on signings:
Meanwhile, Klopp's outlay on players since being appointed by Liverpool in October 2015 sits at around £380 million.
From one angle then, Mourinho arguably has a point. He was outspent by Guardiola and City and could not compete. Meanwhile, he won a UEFA Europa League and Carabao Cup while at United spending a similar amount to Klopp, who has won nothing.
But, the truth is, Guardiola and Klopp have made their spending count by developing fantastic squads.
Their big spending has gone on players who have lived up to their billing—see Ederson, Leroy Sane, Aymeric Laporte for City and Virgil van Dijk, Alisson, Mohamed Salah for Liverpool.
Mourinho, meanwhile, spent big money on the likes of Pogba, Lukaku and Fred, none of whom have yet consistently shown their best at United, which is perhaps a key reason the Portuguese was not given more backing.