The Times says Ronaldo has made the decision to leave due to his desire to play Champions League football for the remainder of his career.
The claims come after Ronaldo was linked with a move to Chelsea last weekend. The Portuguese ace's agent, Jorge Mendes, was said to have discussed a possible move to Stamford Bridge during a meeting with Todd Boehly.
However, United insist Ronaldo is not for sale.
The Manchester Evening News says club sources insist Ronaldo be leaving Old Trafford this summer.
The Portuguese has a year to run on his current contract.