William Carvalho
William Carvalho has a £37m release clause in his contract.Reuters

Manchester United have reportedly agreed a fee in signing Sporting Lisbon star William Carvalho, according to the Mirror.

The 21-year-old is having a £37m buyout clause in his contract. The report claims David Moyes' side are ready to trigger his release clause in order to bring him to Old Trafford at the end of the season.

United are looking to complete the deal before the start of the World Cup as Carvalho is set to become the first of many signings to arrive at Old Trafford in the summer. The defensive midfielder's agent was given a tour of the Red Devils' Carrington training complex earlier this week.

The former Everton man replaced Sir Alex Ferguson last summer and was able to add only one major signing before the start of the current season.

Moyes and Ed Woodward are looking to avoid a similar situation this summer and are looking to make signing in the early stages of the transfer window.

The 50-year-old manager has already admitted that he is hoping most of United's business in the summer is done before the start of the World Cup.

The same report also claims United's league rivals Chelsea are also believed to be interested in signing Carvalho. Meanwhile, Goal.com reports the Old Trafford club's derby rivals Manchester City are looking to make a last ditch attempt at signing the defensive midfielder.

The Citizens have scouted Carvalho in numerous occasions while the midfielder was in action for Sporting last month. City manager Manuel Pellegrini is an admirer of the Portuguese international and is keen on signing him in the summer.

With City and Chelsea in the race, United will face tough competition in signing Carvalho. Meanwhile, the midfielder had earlier hinted a move to Old Trafford could be still on the cards and will make a decision on his future in the summer.

"It's nice being praised and to know there are some big clubs interested in me. [My future could be with] Manchester United or Real Madrid," Goal.com quoted Carvalho as saying.

"It's just nice to have a great European club after me, but at the moment I'm just totally focused on Sporting and doing my best until the end of the season. At the end of the campaign, we will see what happens," he added.