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.
"If we had open slather of course I'd go for Kalyn Ponga because he's an outstanding player but every club has got a salary cap and it is not like the [English] Premier League where you can pay what you want for a player," Seibold said.
"Certainly Kalyn hasn't been in any conversation [with the Broncos]. I think any club in the competition would want someone like Kalyn in their group regardless of what position he plays.
"We certainly haven't spoken about him so I am not sure where that came from. We are guided by a salary cap, so that is pie in the sky sort of stuff."
Photo Getty Images Caption: Newcastle Knights full-back Kalyn Ponga