Louis van Gaal would be interested in bringing Cristiano Ronaldo back to Manchester United, but the manager does not think Real Madrid are willing to sell him.

Speculation that Ronaldo is interested in a return to Old Trafford increased this week when former Real Madrid president Ramon Calderon claimed the Portuguese super star was "fed up" at the club's decision to sell a number of players, including Angel di Maria, who is now playing under Van Gaal.

The United manager did little to quash those rumours at his pre-match press conference today.

When asked whether he could bring Ronaldo back to United, where he enjoyed six successful years, Van Gaal said: "Yes, but it's always a discussion in the papers, and I don't think the media shall buy Ronaldo."

When pushed on the matter again, the United manager said: "It is possible.

"That's what I have said with Falcao. Players like Ronaldo give a lot of extra to a team, but I don't think Real Madrid shall sell him."

Ronaldo won eight major trophies under Sir Alex Ferguson before moving to the Bernabeu five years ago in a then world-record £80million transfer.

The current world player of the year, now 29, hinted last month he would be interested in moving back to his former club.

"I love Manchester and you never know in football. Of course I'm happy at Real Madrid; it's my home, it's my club, but United treated me unbelievably, so you never know," Ronaldo told MUTV before United played Real Madrid during their tour of the United States of America.

"I am still in contact with some people there because I had a good relationship with everybody - it was like my second family."

Senior figures at United have maintained they are willing to back Van Gaal in the transfer market even though he has spent over £150million on six new acquisitions this summer.

And executive vice-chairman Ed Woodward spoke positively about United's finances recently despite the club's failure to qualify for the Champions League last year.

The signings of Radamel Falcao, Di Maria, Ander Herrera, Marcos Rojo, Luke Shaw and Daley Blind have increased competition within the United squad.

The new arrivals have also enabled Van Gaal to change his formation.

United started the season with a 3-4-1-2 system, but Van Gaal played 4-4-2 during the 4-0 win over QPR and his long-term aim is to get the team playing 4-3-3.

Van Gaal has an envious problem in trying to fit the likes of Falcao, Di Maria, Wayne Rooney, Robin van Persie, Adnan Januzaj and Juan Mata into his starting XI.

Only Rooney seems to be safe from being dropped.

"Only the captain has more privileges," Van Gaal said.

"No other player has privileges.

"There are always players we put in the line-up in a team - my captain shall always play."

Van Persie, who is yet to score this season, could be the most vulnerable player in the squad because of Falcao's arrival.

Van Gaal denies having both players in his squad causes problems though.

"I don't think that Falcao interfered with Van Persie or Van Persie interfered with Falcao," the former Holland coach said.

"I think Falcao is a very good striker. I also said when he was coming in his first press conference that I like Van Persie also.

"Then we have Rooney and Januzaj and we have (James) Wilson. We have five players for the two striker positions and I have to choose."

Van Gaal looks set to stick with four at the back for Sunday's game at Leicester, where he hopes to register his second win as United boss.

Chris Smalling is available for the trip to the Premier League newcomers after he recovered from a groin strain.