Under the terms of the release, Holmes will not be permitted to play for any other NRL club in 2019 should his American plans not work out.

The superstar fullback has just returned from a holiday in the US where he is said to have viewed an NFL franchise in the hope of following in the footsteps of Jarryd Hayne, who earned a contract with the San Francisco 49ers in 2015.

"This news brings great disappointment to the Cronulla Sharks, who have worked hard to re-sign Holmes to a five-year extension, which would have made him the highest-paid player in the club's history," the Sharks said in a statement on Tuesday.

"While this is in no way the outcome the club planned for, there was no option but to grant a release to Holmes."

Holmes acknowledged the Sharks' understanding and support of his decision, while confirming he would enter fresh discussions with the club about his rugby league career if his American dream doesn't pan out.

"I will be forever grateful to the Cronulla Sharks Football Club and the Sharks fans for the past five years of support," he said.

"It was a special moment we all shared winning the club's first ever NRL premiership (in 2016)."

NRL chief executive Todd Greenberg wished Holmes good luck, but said the 23-year-old was taking a "big risk" walking away from his million-dollar annual salary in rugby league.

But grand final-winning former teammate Luke Lewis and former South Sydney junior Jordan Mailata, drafted this year by the Super Bowl-winning Philadelphia Eagles, are among those backing Holmes to make a successful transition to American football.

While Holmes is yet to field any formal offers in the US, Lewis believes if anyone is capable of pulling off such an audacious move, it's the record-setting Kangaroos flyer.

"One thing with Val is he's a very lucky young kid. He's got the world at his feet to be honest," Lewis told the Macquarie Sports Radio breakfast show.

"He loves his NFL and, if an opportunity like that comes up, you'd be mad to turn your back on it.

"If that's what he wants to do, if anyone can do it, it's definitely Valentine."

A freakish athlete with a knack to the line, Holmes' release comes less than 12 months after he bagged 11 tries in two games for Australia at the 2017 World Cup and two years after he impressed NFL scouts during an off-season reconnaissance trip to the US.

"He's a super talented athlete," said Cronulla co-captain Wade Graham, who wouldn't begrudge Holmes the opportunity to chase his dream.

"Physically, I have no doubts he can match it with them over there."

Talent apart, time is also on Holmes' side.

While Hayne was 26 when he made the move from Parramatta, Holmes only turned 23 in July.

"(It's a) perfect opportunity, perfect timing for Valentine to go over and do what he wants to do and, if it doesn't work out, he can come back and still earn the money he wants to earn," Lewis said.

"I think if he does make it we'll see a lot of other guys put their hands up and want to go over as well."

Australian Associated Press