Spanish league sources confirmed on Tuesday that Manchester United goalkeeper David de Gea hasn't been registered as a Real Madrid player as his prolonged transfer collapsed after the Spanish transfer window closed on Monday.

"The player is not registered," a spokesperson for the Spanish Professional League (LFP) said when contacted by AFP on Tuesday.

Madrid refused to confirm reports that the player's contract had been lodged with the league after the deadline at midnight local time (2200GMT) after a deal had been struck between the two clubs at the last minute.

"Until now we haven't been notified of anything," said a spokesperson for the club.

Real seemed set to conclude the long-running transfer saga with a deal that would see the Spanish giants pay up to 30 million euros ($33.5 million, £21.8 million) for De Gea, with Costa Rican international goalkeeper Keylor Navas moving to United for a fee in the region of 15 million euros as part of the deal.

Initial reports suggested that the documentation needed to formalise the transfer wasn't completed before the Spanish transfer window closed, but that Madrid hope proof of an agreement between the clubs will be enough to push the deal through.

"Everything has been cancelled unless there is an unexpected turnaround," Madrid sports daily AS said on Tuesday.

"The Spanish goalkeeper's contract didn't arrive in time with the league.

"The first reports suggested that United had sent the required documentation late, but Madrid are sure they have proof that shows the English club sent the documentation at 2359 and that they sent it just after to the league."

FIFA refused to comment on the specific details of the case when contacted by AFP on Tuesday, but did confirm that there are lines of appeal open should the clubs try to still conclude the deal.

"We're working closely with TMS (Transfer matching system) a subsidiary firm of FIFA and liasing with them."

De Gea has just one year left on his contract at Old Trafford meaning he could join Madrid for free next year if the transfer doesn't go through now.

The Spanish press slammed Madrid's failure to deliver their prized target in the transfer market this summer with the front pages of sports newspapers Marca and Sport describing the situation as "ridiculous."

The Spanish international hasn't featured in any of United's six games so far this season with manager Louis van Gaal claiming the 24-year-old wasn't focused at the English giants due to Madrid's interest.

The 10-time European champions were in the market for a goalkeeper after Spain captain Iker Casillas ended his 25-year association with the club by moving to Porto in July.

De Gea joined United from Real's city rivals Atletico Madrid in 2011 and despite a shaky start went on to shine, winning the club's fans' and players' player of the year awards for the past two seasons.

However, he refused to sign a new deal with United due to his desire to return to Spain with Real.

A standoff between the two clubs ensued with United also expressing their interest in Real captain Sergio Ramos over the summer before he ended speculation over his future by signing a new five-year deal with Los Blancos.