MADRID (AP) — The deadline arrived, but the announcement never did.

In a surreal ending to the transfer window in Spain, the much-anticipated move of Manchester United goalkeeper David de Gea to Real Madrid never materialized. The clubs had struck a deal that would see Madrid goalkeeper Keylor Navas move the other way, but it broke down because the necessary paperwork wasn't submitted on time.

Madrid and United negotiated late into Monday evening after talks that dragged on for several weeks, but the clubs failed to register the new contract with the Spanish league offices before midnight local time.

La Liga confirmed Tuesday that De Gea was not among the players who transferred by Monday's deadline, but did not say whether Madrid actually attempted to register the player or if something went wrong to keep the deal from happening.

The bizarre breakdown quickly became the object of fan derision and mockery. It left many wondering what exactly went wrong — and how two of world football's biggest clubs could mess things up so badly.

Madrid and United blamed each other for the debacle.

Madrid said the English club took too long to review the transfer contracts and was late submitting the required documentation into FIFA's electronic transfer system. In its lengthy statement, Madrid also blamed United for delaying the start of the transfer talks.

"Manchester United did not agree to open any negotiations over the federative rights of David de Gea until yesterday (Monday) morning," the Spanish club said. "Real Madrid, despite the difficulties entailed in carrying out a deal of these characteristics on the final day of registration, agreed to initiate these talks."

But United said that Madrid's first bid for De Gea did not arrive until Monday lunchtime. In a lengthy statement on the timeline of events, the English club said:

— With more than two hours to go in the transfer window, United sent the transfer documents for both De Gea and Navas to Madrid. But with 28 minutes to go, Real returned De Gea's documentation without the signatory page.

— Twenty minutes before the deadline, "major changes to the documentation came through to Manchester United which immediately put the deals at risk."

— With five minutes to go, the documents required to cancel De Gea's contract were received by United but not those for Navas. Three minutes later, the De Gea transfer documents were uploaded to FIFA by United but not by Madrid in time.

The Premier League club ended its statement by saying: "Manchester United acts appropriately and efficiently in its transfer dealings. The club is delighted that its fan-favorite double player of the year, David de Gea, remains a Manchester United player."

Under FIFA rules, both clubs must send in all the required documentation to its electronic transfer system before they can register the new contract with the national federation. FIFA said it could not comment on whether both clubs had submitted the information correctly because all transfer documents are confidential.

Madrid said United finalized the deal with Navas seven minutes before the deadline, and only submitted the information on the De Gea transfer exactly at midnight. The Spanish club said it only had access to that information two minutes past the deadline.

"In short, Real Madrid did everything necessary at all times to complete both transfers," the club said.

Spanish newspaper Marca said Navas, who had been reluctant to leave Madrid, arrived at the Santiago Bernabeu with his agent to finalize details of the contract with United just minutes before the deadline.

Madrid fans had been praising Navas recently, while many criticized the club's decision to try to sign De Gea. The crowd at the Santiago Bernabeu on Saturday loudly chanted Navas' name after he saved a penalty in the 5-0 rout of Real Betis in the Spanish league.

It was unclear whether the clubs could or would appeal to league authorities or FIFA in an attempt to push the deal through. The English transfer window remained open through Tuesday.

The failure to finish the deal should create a difficult situation for the De Gea, who could be forced to return to United despite having been dropped from the team by manager Louis van Gaal as the talks dragged on. Van Gaal had said the Spanish goalkeeper had his heart set on a move back to his hometown.

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AP Sports Writers Rob Harris in London, Steve Douglas in Manchester, England and Graham Dunbar in Geneva contributed to this report.

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Tales Azzoni on Twitter: http://twitter.com/tazzoni