Storm officials are optimistic 20-year-old Duffie, off contract at the end of the season, will accept their offer.
They will give the Kiwi time to weigh up what is believed to be a bigger offer from the Eels, where former Storm assistant coach Stephen Kearney is in charge.
Duffie is also close to Kearney’s assistant Brad Arthur, who coached him in the Storm’s 2009 under-20s premiership-winning team.
In the Storm’s favour is Duffie’s relationship with their players, particularly housemate and fellow winger Justin O’Neill, who re-signed with the Storm last season.
Duffie is back in full training after a shoulder injury.