Anthony Seibold has dismissed talk of Brisbane Broncos potentially signing Newcastle Knights star Kalyn Ponga as "pie in the sky sort of stuff".

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."