The report claims United have launched a feasibility study to establish whether could actually fund a move for the Portugal international. Sir Alex Ferguson sold Ronaldo to Real Madrid for a world record £80m in the summer of 2009.
But United could expect to pay less than that figure to bring Ronaldo back to Old Trafford because the Portuguese star is now 28, and only has just over two years left on his Real Madrid contract.
As a result, the report suggests a fee in the region of £60m would be considered enough. However, the player's wages would take the total outlay required to resign Ronaldo to well over £100m.
Manchester City remain interested, but Ronaldo's United past complicates matters. Add the fact that Ferguson retains a first-option clause on Ronaldo, and it's difficult to see the 2008 Ballon d'Or winning moving to anywhere other than Old Trafford.
The forward's commercial value could make a deal worthwhile for the Premier League leaders', and the report claims United are currently determining the extent to which any transfer would pay for itself through increased sponsorship and shirt sales.
Chief executive David Gill is set to step down in the summer, and his replacement Ed Woodward is believed to be keen to make a high-profile summer signing at the end of the season. To fund a move, Woodward is thought to be willing to court further sponsors to boost the Old Trafford coffers.
Another option remains using United players Real Madrid are interested in signing themselves as carrots to tempt the defending La Liga champions into selling Ronaldo.
David De Gea, Nani and Javier Hernandez have all been linked with moves to the Bernabeu, and the Daily Mail suggests a player-plus-cash deal could be favoured by United as it would make the Ronaldo move cheaper.
The report concedes that plans are still very early stages, but Ronaldo's public declaration of unhappiness earlier this season has encouraged United.
Madrid president Florentino Perez is up for reelection in June, which could prompt Real Madrid into a summer spending spree.
Talks have already opened regarding the transfer of Edinson Cavani to the Bernabeu, while Gareth Bale remains a top target for the Spanish giants. To finance a move for one, or both, Ronaldo could be available.