Diarra will undergo tests in the Spanish capital before signing a contract to complete his move to the Bernabeu club, who have already confirmed Ajax striker Klaas-Jan Huntelaar as a transfer-window recruit.

It remains unclear whether Madrid will include Diarra in their plans for the Champions League last-16 clash with Liverpool.

UEFA rules would allow Madrid to register him, despite his involvement in Portsmouth’s UEFA Cup campaign.

But clubs are permitted to register only one player for the knock-out stages who has played in Europe for another club in the same season, and Huntelaar was involved with Ajax in the UEFA Cup and may get the nod.

Diarra, 23, will reportedly cost the Primera Liga giants around £20million and Madrid have confirmed he has agreed to a four-and-a-half-year contract.

The France international scored three goals in 31 appearances for Portsmouth,

Diarra is expected to earn an immediate starting spot at the Bernabeu with fellow defensive midfielders Mahamadou Diarra and Ruben de la Red both ruled out for the season.

He will work under new Madrid coach Juande Ramos, the former Tottenham boss, who was placed in charge until the end of the season following the sacking of Bernd Schuster earlier this month.

The deal represents good business for Portsmouth who signed Diarra from Arsenal in January for a fee thought to have been around £5m.