MADRID, July 1 (Xinhua) -- Chelsea have signed Real Madrid's Croatian international midfielder Mateo Kovacic on a deal worth about 40 million pounds (50.5 million U.S. dollars).

Chelsea are able to sign Kovacic despite a two-transfer window transfer ban from FIFA, because they already held the player's registration after he spent last season on loan with them from the Spanish club.

Real Madrid confirmed the deal on their official website on Monday, saying: "Real Madrid and Chelsea have agreed the transfer of the player Mateo Kovacic."

"The club wishes to thank Kovacic for these years of commitment, professionalism and exemplary behavior, and wishes him good luck in his next step," continued the statement.

Although Kovacic produced some slightly irregular form during his first season at Stamford Bridge, his signing will ensure Chelsea have midfield cover as England international Ruben Loftus-Cheek recovers from a ruptured Achilles tendon which he suffered at the end of last season.

Real Madrid will also be grateful for the transfer fee after already spending over 300 million euros on players (including Eden Hazard from Chelsea) this summer.