The experienced midfielder is currently a free agent after seeing a previous contract with the Cottagers expire at the end of last season.
He has been allowed to train with the Premier League club and work his way back from a serious knee injury.
Former Fulham boss Martin Jol was prepared to keep the door open for a possible first team return, and new coach Rene Meulensteen has ruled nothing out.
Diarra is, however, struggling to prove that he is deserving of fresh terms.
He was able to make a return to action in an U21 clash with Reading in September, but suffered another setback shortly afterwards.
It has been suggested that other clubs will look to make a move in the New Year if Fulham continue to stall, with Crystal Palace said to be among them, but Meulensteen doubts any offers will be tabled in the immediate future.
He said in the Fulham Chronicle: "He is still recovering. He is nowhere near (full fitness)."