Portsmouth: Diarra to move to Real Madrid
British media reported the Spanish champions would pay about £20m for the 23-year-old, although Portsmouth have yet to confirm any transfer details.
"We have always said that we would only allow our players to leave if we received an exceptional bid," a spokesman said on the south-coast club's website.
"We could not stand in the way of a move such as this for Lassana," they added.
Diarra joined Chelsea in 2005 from then-Ligue 2 club Le Havre, and has since won the FA Cup twice, first with the west London club in 2007 and then with Portsmouth in May.
The midfielder, who has played 16 times for France, moved to Arsenal in August 2007 before joining Portsmouth in January.
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