Liverpool have been cleared by Fifa to sign Javier Mascherano from West Ham.
The Reds needed clearance from world football's governing body to sign the Argentina midfielder, because he had already played for two clubs, West Ham and Corinthians, competitively this season.
The Argentinian has failed to make an impact at Upton Park, after joining the Londoners on the final day of the summer transfer window along with compatriot Carlos Tevez.
A statement from Fifa this morning read: "After due consideration of all aspects, the Fifa single judge ruled that 'upon registration for Liverpool FC during the present registration period, the player Javier Mascherano is eligible to play in official matches with the said club with immediate effect'."
Liverpool are believed to be taking the player on loan with a view to a permanent deal.
The ruling by Fifa appears to take into account the fact that the Brazilian and English seasons do not run parallel, with the Campeonato Brasileiro beginning in April and ending in December - thus cutting through the close season in this country.
The Fifa statement continued: "Particular emphasis was given to the safeguard of the sporting integrity and the crucial element of overlapping sports seasons between associations, notably in cases in which a sports season starts prior and ends beyond July 1st.
"Yet, the single judge made it clear that such permission can only be granted under very restrictive preconditions, such as they exist in the case at stake, yet never occurred in a case that was submitted to the attention of the competent deciding bodies at an earlier stage.
"In particular, he emphasised that a series of elements related, on the one hand, to the duration and the positioning of the relevant sports seasons as well as to the respect of the registration periods and, on the other hand, to the duration and respect of the employment contracts concerned, need to be cumulatively met."
Mascherano, 22, first came to worldwide attention while playing for Argentinian club River Plate.
He was signed by Corinthians along with Tevez, after Media Sports Investment (MSI) bought a controlling stake in the Sao Paulo club.
Mascherano had an impressive World Cup with Argentina and arrived at West Ham in a shock double deal with Tevez at the end of August. It was thought at the time that their arrival was a prelude to businessman Kia Joorabchian - a key player in MSI which still held the registration for Tevez and Mascherano - taking over the Hammers.
However, Joorabchian lost out to an Icelandic consortium headed by Eggert Magnusson - and Mascherano struggled for playing time, starting just five games.
