Serbian international midfielder Nemanja Matic signed for Manchester United on Monday from Premier League champions Chelsea, the buying club announced, for a reported fee of £40 million ($52.7m, 44.7m euros).

It is the second time United manager Jose Mourinho has invested in the 28-year-old's talents having brought him back to Chelsea in 2014 after a successful spell with Benfica.

Matic signed a three-year contract with United with the option to extend it by a year.

"Nemanja is a Manchester United player and a Jose Mourinho player," Mourinho told the club website.

"He represents everything we want in a footballer: loyalty, consistency, ambition, team player.

"I would like to thank him for his desire to join us because without that, it would be impossible to have him here. I am sure our players and supporters will love him."

Matic played just 65 minutes for Chelsea in his first period at the club before being part of the deal that saw David Luiz move to Chelsea and him move in the opposite direction to Benfica in 2011.

He said Mourinho's presence at United had made it an easy decision.

"I am delighted to have joined Manchester United. To work with Jose Mourinho once again was an opportunity I couldn't turn down," he told the club website.

"I have enjoyed my time at Chelsea and would like to thank the club and the fans for their support. I cannot wait to meet my new team-mates and to start training with them.

"This is a very exciting time for the club and I am looking forward to playing my part in creating more history for this great club."

Matic's arrival takes Mourinho's spending to almost £150m in the close season having outlaid £31m for Swedish defender Victor Lindelof from Benfica and £75m on Belgian international striker Romelu Lukaku from Everton -- though that could rise to £90m with add-ons.

Ironically Lukaku's deal almost put a spike in Matic's transfer to United as Chelsea had ear-marked the striker as their number one target and were not best pleased when he was snatched from underneath their noses.

At one point it was thought the Serbian, who had found life increasingly difficult at Stamford Bridge competing with French star N'Golo Kante for the central midfielder role, would end up at Juventus instead.

However, once United were quoted £50m for England defensive midfielder Erik Dier by Tottenham they switched their attentions back to Matic and Chelsea relented.

Matic enjoyed a far happier second spell at Chelsea than his first one, winning the Premier League title twice and while never a prolific goalscorer he scored one of the goals of last season in the FA Cup semi-final win over Spurs at Wembley.

In all he scored seven times in 154 appearances for Chelsea.

"The Serbian departs Stamford Bridge having played a pivotal role in two Premier League title triumphs, as well as winning the League Cup with the Blues," said Chelsea in a long farewell statement.

"These trophies all came in his second spell at the club, after re-joining Chelsea in early 2014 to add steel and strength to the midfield.

"We thank Nemanja for his fantastic service and wish him well for the future."

Mourinho's spending may not be over yet as he is known to cherish Croatian winger Ivan Perisic who is at Inter Milan but United baulked at the initial demand of £48.5m although they hope the Serie A side might lower their price.