"Looks like I'm on the hit list," Williams wrote on Twitter. "I'm not gonna hate on this guy at all as I respect what he's done.
"I also really respect his skillset as a boxer. But if he wants some he can get it!
"Yours respectfully - your first loss."
A fight between Paul and Williams appears on the surface to be unlikely, with Williams lacking name recognition in America, despite being one of the biggest sports stars in Australia and New Zealand.
In the last three years, Paul (5-0) has quickly become one of boxing's biggest draws thanks to his massive social media following.
In his most recent fight, the 25-year-old claimed a spectacular knockout over former UFC champion Tyron Woodley in their big-money rematch last year.
Williams, who is 9-0 in the ring, is giving boxing one last push in the twilight of his professional sporting career and recently trained in the UK with former world champion Andy Lee, where he sparred with the likes of Tyson Fury and Joseph Parker.
Before his fight against Hall, Lee even suggested Williams has the potential to challenge for a world title.