Several clubs have shown an interest in the 25-year-old, who has represented Cook Islands, but the Bulls insist they want to retain their best players.
“Leeds made an approach, through the correct channels, for Keith’s services but we rejected their offer out of hand,” said Bulls manager Stuart Duffy.
“Keith is happy at the club and has been informed of the Rhinos interest. We have absolutely no intention whatsoever of letting our best players leave and were happy to decline the Rhinos offer.”
However the club will be without winger, Shaun Ainscough who has snubbed an offer of a reduced contract in favour of trying his hand in Australia.
“It’s a massive decision to make but I just couldn’t stay at Bradford,” he told the Bradford Telegraph and Argus. “I wanted to but once I’d added everything up, I’d have been scraping by.
“I sat down with the missus to go through the finances and once we’d paid all the bills there was only enough left for food, nothing more.
“I was still going to take their offer right at the end but it just didn’t add up. I’m gutted to go but that’s just how it is. It was the hardest thing I’ve had to do in my life.”
Meanwhile, Gareth Hock could be the latest English player to try his hand in the NRL, after Australian club Parramatta confirmed they were discussing a possible move.
Former GB international, Bobbie Goulding sparked speculation on Twitter, before club officials stated their interest.
“I can confirm we are in discussions only, at this time,” said Eels chief executive Ken Edwards.
Wigan would require a significant fee to release the 29-year-old forward who was handed a long-term contract after returning from a doping ban earlier in the season.
If he does decide to depart, he will become the fifth player to move to the NRL this season, a number which could rise to six should centre George Carmont postpone his retirement for a one year stint at New Zealand Warriors.
Carmont is currently pondering the possibility of taking up a mentor role, while it is also understood Leeds are interested in his services.
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