Knights chief executive Philip Gardner this week stated that the Broncos are a "bigger" threat than New Zealand Rugby as he strives to tie Ponga down to a new deal.
The 21-year-old Queensland State of Origin full-back, who has made no secret of his desire to play for the All Blacks, is contracted until the end of next year, so he will be a free agent to NRL clubs on November 1 if Newcastle cannot agree an extension.
Broncos coach Seibold rates Ponga highly, but says salary-cap restrictions would make a move for the livewire Knights man unlikely.
