The Portugal talisman quit Real Madrid before the start of this season, opting to join Juventus.
The Red Devils were linked with a move for their former talisman, with United executive vice-chairman Ed Woodward keen to reunite with the 33-year-old.
However, according to the Daily Mirror, Mourinho told United transfer chiefs not to sign Ronaldo following his Real exit.
They say the Special One demanded United sign defensive reinforcements rather than pay around £100m for Ronaldo, who would have pocketed in the region of £500,000-a-week at Old Trafford.
However, Mourinho’s demands were not met as United failed to sign a new centre-back.
Toby Alderweireld, Harry Maguire and Diego Godin were all targets for Mourinho, however, Woodward refused to pay up in the transfer window.
The Mirror add that Mourinho is still furious with Woodward for not backing him this summer.
Woodward’s willingness to move for an ageing Ronaldo this summer enraged the United boss even more.
The Red Devils welcome Ronaldo back in October when Juventus travel to Old Trafford in the Champions League.
Speaking about United’s struggles at the start of this season, which has seen Mourinho’s men lose to Brighton and Tottenham, the Red Devils boss said: “I said in the summer what would happen, before the competition started.
“I knew this was going to be difficult because I also knew that last season was very, very difficult.
“The teams that are really, really good offensively are the teams that are very very solid from the back.
“Teams that have the offensive mentality are also ultra-confident defensively.
“Against Spurs were were really positive and really strong and I think a very good opponent felt they were really in trouble but two defensive mistakes in five minutes lost the game for us.
“It’s a process and it’s a process that has risks – especially if you make the defensive mistakes that breaks that dynamic.
“Two defeats are two defeats. We still have 35 matches to play. But our realistic target now is to win on Sunday. After that it will be to win against Watford.”