Kane has been in prolific form for the north Londoners since breaking into the first team in 2014 and has claimed the coveted Premier League Golden Boot for the last two seasons, which will have impressed Mourinho no end, particularly given his side's goal-shyness in the last campaign.
Spurs have vowed to keep hold of their star players, including Kane and Dele Alli, and the fact the former is under contract until 2022 puts them in a strong position as they fight to keep hold.
United were linked with a stunning move for Ronaldo after reports emerged suggesting the 32-year-old Portuguese superstar wanted to leave Real Madrid after being accused of tax evasion in Spain.
At the opening of the transfer window, Sarah Winterburn of Football365 opined that Manchester United should scrap any and all striking targets and focus purely on the acquisition of Harry Kane.
How much is a player like Cristiano Ronaldo or Lionel Messi really worth?
Old Trafford boss Mourinho has made it clear he would prefer a move for striker Kane rather than an attempt to bring Ronaldo back to Manchester.
It would take a world-record bid to get him away from Spurs with £100m mentioned as United's potential offer.
Alex Apati of Ladbrokes explained: "It's early days, but such a drastic fall in odds overnight tells us all we need to know here".