West Ham have agreed a transfer fee with Liverpool over the permanent transfer of Andy Carroll.
West Ham have confirmed the free-transfer signing of Romanian full-back Razvan Rat on an initial one-year deal.
The Malian, whose former clubs include Real Madrid and Monaco, joined the Cottagers as a free agent in January until the end of the season.
That deal included an option to extend his stay for another year, with the club confirming that the clause has now been activated.
Diarra made 11 appearances last season as Fulham finished ninth in the Barclays Premier League.