The 37-year-old forward has reportedly informed the Red Devils of his wish to move on once again during the transfer window, despite re-signing for the club just 12 months ago.
A lack of Champions League football, as well as a slow start to United's transfer plans under new boss Erik ten Hag, are said to have prompted the Portugal international to seek opportunities elsewhere ahead of the 2022-23 campaign.
United have so far signed just one player ahead of Ten Hag's debut Premier League season - Tyrell Malacia from Feyenoord - although deals for Christian Eriksen, Frenkie de Jong and Lisandro Martinez remain in the pipeline.
The Dutchman had prioritised the centre of midfield for strengthening this summer, which he hopes his former player De Jong, and free agent Eriksen, can fill, with a right-back and central defender next on the agenda originally.
However, according to Manchester Evening News, the potential exit of Ronaldo has forced United and Ten Hag to switch their focus to attacking reinforcements once the central midfielder targets have been secured.
The Old Trafford club were said to be keen to strengthen in the forward areas regardless during the transfer window, but the possible loss of last season's top goalscorer has forced Ten Hag to prioritise in the final third ahead of his back line.
The report continues with United's allowance to sanction a move for Aaron Wan-Bissaka in the coming weeks, but a move for a potential replacement, and competition for Diogo Dalot, look set to be put on hold as a result of Ronaldo's desire to leave.