Gremio midfielder Arthur Melo has previously stated his desire to join Barcelona. Getty

Barcelona already possess one of Europe’s best midfield units, but they are continuing to strengthen with an eye on the future and have secured first option to sign Gremio midfielder Arthur Melo.

Ernesto Valverde already has Sergio Busquets, Paulinho, Andres Iniesta, Philippe Coutinho, Ivan Rakitic and Andre Gomes at his disposal, and they have played a key role in Barcelona’s dominance in the La Liga this season — they are currently eight points clear of Atletico Madrid in second place.

The Spanish giants, however, are keen to sign the best talent available and have agreed on a deal for Arthur, who is highly rated in Brazil. The central midfielder played a key role in helping Gremio win the Copa Libertadores for the first time in over two decades.

Barcelona, after intense negotiations, which have been going on since February, agreed to a deal which gave them first option to buy the midfielder. But, they are also entitled to activate the option in the summer, and will have to meet the agreed buyout clause which is set at €30m ($37m) plus €9m in variables based on his appearances and success with the Catalan club.

“FC Barcelona and the Brazilian club Gremio de Porto Alegre have reached an agreement on a purchase option for the player Arthur Henrique Ramos de Oliveira Melo, whereas FC Barcelona may exercise this right on the player's federative rights during July of 2018,” a statement read on the Spanish club’s official site. “In the event that the Club finally exercises the option signed, the price of the transfer is set at €30m plus €9m in variable amounts.”

Gremio were keen to keep Arthur at the club at least until January 2019, which would have allowed him to play another season. But, Barcelona reportedly wanted to bring him to the Camp Nou at the earliest in order to allow the midfielder to settle into his new surroundings.

The Spanish giants have heaped praise on the midfielder ahead of his potential move, labeling him a player “known for his passing ability.”

“Arthur is a midfielder who is known for his passing ability. Another of his qualities is his ability to lose his man, a factor that makes him a danger close to the opponents’ area,” the statement added. “The Brazilian is excellent at protecting the ball and can come up with the final pass in the final third.”

However, according to ESPN, Barcelona will face one issue if they were to sign him in the summer. According to La Liga rules, every club can only have three non-EU players in the squad and their roster is currently full with Coutinho, Paulinho and Yerry Mina.

The report claimed they were working on a solution which will see Coutinho acquire a European passport through his girlfriend, and will allow them to sign Arthur in the summer. If the move goes through, the Gremio midfielder is expected to sign a five-year deal.