Ronaldo is seeking to leave United in order to play Champions League football this season.

His agent Jorge Mendes has spent the summer exploring potential options for the 37-year-old, who still has one remaining on his current contract at Old Trafford.

United have continued to state that Ronaldo is not for sale but behind the scenes there is a growing feeling that it might be better to cut ties with the five-time Ballon d’Or winner this summer, rather than forcing him to stay for the final year of his deal.

While United could be softening their stance, Ronaldo’s options appear to be limited.

According to CBS Sports, Bundesliga club Borussia Dortmund remain the only credible option still on the table for the Portugal international.

The German giants, who are able to offer Ronaldo Champions League football this season, are said to be considering a late move for the forward.

Ronaldo is seeking a move away from United this summer (Image: Alamy)Dortmund are holding “internal talks” over a potential bid to sign the Portuguese star either on a permanent deal or on loan.

Dortmund are keen to bring in another striker before the window closes after new signing Sebastien Haller was ruled out for several months after being diagnosed with a testicular tumour.

Manchester United have also been linked with a move for Dortmund right-back Thomas Meunier but it is believed the Belgium international is not being discussed in relation to a potential deal involving Ronaldo.

CBS Sports claim sources “close to Ronaldo” view Dortmund as the striker’s “last option” to leave United this summer.

United are interested in Dortmund right-back Thomas Meunier (Image: Alamy)The report also claims that Sporting manager Ruben Amorim is firmly against the move, believing Ronaldo would not be a good fit for his team.

It is also claimed that Atletico Madrid have now ended their interest in the former Real Madrid star, following a backlash from fans over the proposed transfer.

“They know the truth when they interview in a couple weeks. The media is telling lies,” Ronaldo wrote on Instagram.

“I have a notebook and in the last few months of the 100 news I made, only 5 were right. Imagine how it is. Stick with that tip.”