Rooney is said to be furious at the comments of manager David Moyes, who during an interview last week appeared to indicate he regarded the 27-year-old as back-up to last season's top scorer Robin van Persie.
Moyes is not thought to be happy about the situation, believing his comments have been taken out of context.
Nevertheless, he can hardly deny saying them nor dispute they have gone down incredibly badly with Rooney, whom sources told Press Association Sport is "angry and confused" about his treatment.
As far as the 27-year-old is concerned, he is at the peak of his career and has no intention of playing second fiddle to anyone, or being reduced to the rank of a squad player.
With four Premier League titles and a Champions League winner's medal to his name, Rooney does not believe he has anything to prove at United.
Yet he feels as though he has been put on trial by Moyes at a time when he should be concentrating his efforts on recovering from the hamstring injury that saw him sent home from United's pre-season tour within hours of landing in Thailand on Thursday.
After months of speculation about his future, and no statement of intent to stay from the player, it is now clear that unless there is some major repair work undertaken, Rooney will be leaving.
The manner of United's response is the first major test for Moyes and chief executive Ed Woodward since they replaced Sir Alex Ferguson and David Gill respectively at the beginning of the month.
Chelsea are thought to be monitoring the situation, with manager Jose Mourinho having recently expressed his admiration for Rooney.
The Portuguese also offered his thoughts on Rooney's position as a starting player for United, saying if he played second fiddle to Van Persie, it could have implications for England and international boss Roy Hodgson in World Cup year.
Rooney, who was left out of key games for United last season by Sir Alex Ferguson, departed Bangkok as Chelsea arrived in Thailand after a hamstring injury ruled him out of the tour of Asia and Australia.
"If Wayne is a second choice for Man Utd, then the national team will be affected," Mourinho told BBC Sport.
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- David Moyes