Barcelona expect to complete the surprise signing of Leganes' Martin Braithwaite on Wednesday after being given permission to bring in a forward outside the transfer window, sources have told ESPN.

Barca will give the striker's €18 million buy-out clause to La Liga if Leganes, who sit in the relegation zone in Spain's top flight, stick to their stance that they are not willing to negotiate.

The Madrid-based club lost another frontman, Youssef En-Nesyri, to Sevilla in January and do not want to lose Braithwaite as well.

Braithwaite, 28, has already agreed terms with Barcelona and is expected join his new teammates immediately. He could make his debut on Saturday against Eibar.

Leganes will not be able to sign a replacement. Barca were given permission to turn to the transfer market by La Liga after losing Ousmane Dembele to injury for the rest of the season, but the same rule does not exist for clubs who see a player leave through their release clause.

La Liga maintains the right to authorise signings outside of the transfer window, which closed in January, on a case-by-case basis. The legislation states that if a player is ruled out for at least five months, a replacement can be signed.

Barca had previously explored the possibility of signing Real Sociedad's Willian Jose, Real Betis' Loren Moron, Alaves' Lucas Perez and Getafe's Angel Rodriguez, but, for different reasons, did not push forward with their interest in any of the quartet.

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A loose agreement had been struck with Getafe for Angel over the weekend, but Barca coach Quique Setien's insistence on Braithwaite led the club to take a different path. Setien values the fact Braithwaite can play wide or through the middle and is four years Angel's junior.

Braithwaite first joined Leganes in January 2019 on loan from English side Middlesbrough before making the move permanent during the summer for €5m. He has scored 13 goals in 41 appearances for the club.

He has also had two spells in France, first with Toulouse, who he joined from Esbjerg FB and later with Bordeaux on loan. He has been capped 39 times by Denmark, scoring seven goals.

Barca were given the green light to make a signing on Monday after La Liga ratified the severity of Dembele's injury. The Catalan club had filed a request to the league last week for permission to sign a new player after he underwent surgery on a torn hamstring in Finland, leaving him sidelined for six months. They are also without striker Luis Suarez for the next two to three months due to a knee problem.

Barcelona are only allowed to bring in a player already registered to play in the Spanish or someone without a club, which led them to Braithwaite. The Denmark international will freshen up Setien's attacking options, which are currently limited to Lionel Messi, Antoine Griezmann and B team winger Ansu Fati.