The highly-rated 19-year-old joined the Cottagers last year - when they paid Portsmouth more than £250,000 for his signature.
The Australian youth international is yet to play for Fulham and they are now sending him to the Priestfield Stadium to gain some first-team experience.
Gillingham are expected to confirm his capture on Thursday with a view to him making his debut against Dagenham & Redbridge at the weekend.
Williams, is the younger brother of Middlesbrough captain Rhys and also has a twin brother, Aryn, who is playing for Burnley.







