Manchester United continue to doubt reports that Cristiano Ronaldo wants to leave Real Madrid to return to Old Trafford, sources close the Premier League club have told ESPN FC.

Spanish newspaper AS reported on Monday's front page that the Portugal star feels betrayed by the Spanish giants for not getting an improved contract. A source close to Ronaldo told ESPN FC that report was accurate on Monday night.

However, sources close to United remain unconvinced Ronaldo has any real desire to leave Real Madrid and is merely trying to force a better deal out of his current club.

The reaction out of United was similar to a response last June, when sources also said United were yet to be convinced that Ronaldo is prepared to move.

AS reported Ronaldo has already told several Real teammates of his intention to leave Madrid at the end of the season and of his wish to continue his career at Old Trafford, after Madrid president Florentino Perez promised Ronaldo a new contract shortly after he helped Los Blancos retain the Champions League last season.

In November 2016, Ronaldo signed a new contract until June 2021 and said it would not be his last as a player. The 32-year-old forward admitted in December after scoring Real's winner in the Club World Cup final against Gremio that he "would like that [pay-rise] but it does not depend on me."

Buenos días, aquí tenéis la #PortadaAS del 15 de enero de 2018 pic.twitter.com/Mh9WyUNS4H — AS (@diarioas) January 15, 2018

A report in the El Pais newspaper this weekend said the lucrative contracts signed by Neymar and Lionel Messi last year at Paris Saint-Germain and Barcelona, respectively, have left Ronaldo urgently wanting a better deal.

The five-time Ballon d'Or winner has scored 422 goals in 418 official games for Real, including a brace against Juventus in Real's 4-1 victory in the Champions League final back in June.

But he is in the midst of his worst La Liga campaign since he arrived to the Bernabeu stadium in 2009, with his worst numbers since December 2005 when he only scored one goal for the Red Devils.

Ronaldo has scored 16 goals this season in all competitions but just four in La Liga, where Real are fourth in the standings, 19 points adrift of leaders Barcelona at the halfway point of the season.

Ronaldo has failed to score in Real's last three league games, including Saturday's 1-0 home defeat to Villarreal, leading some media outlets, among them Marca, to question why coach Zinedine Zidane insists on starting the same players every week while Ronaldo is making "too many incredible mistakes."

However, former Real Madrid player and coach Bernd Schuster told Onda Cero radio that he believes that Zidane faces a difficult dilemma to bench Ronaldo.

"I'm sure Zidane also considers benching Cristiano but how do you tell him [Ronaldo]," Schuster said. "It's not that easy. You have to analyse what the real problems are. There is a lack of goal. If your leading scorer has scored four then that is a problem. That is fundamental."

ESPN FC's Manchester United correspondent Rob Dawson and La Liga writer Adriana Garcia contributed to this report.