Declaring himself in career-best form and capable of winning the US Open, Marc Leishman has shot down the notion LIV golfers can't compete for the sport's greatest spoils.

Leishman will return to major championship golf for the first time in almost three years at next week's US Open in Pennsylvania after surviving 38 gruelling holes to qualify on Monday.

The 2015 British Open runner-up will join fellow Australians Jason Day, Min Woo Lee, Adam Scott, Cam Davis and Cameron Smith at Oakmont Country Club, where Leishman is a member and finished tied for 18th in 2016.

Having also broken through for his maiden victory on the Saudi-backed breakaway league in Miami in April, the 41-year-old insists he isn't teeing up at the season's third major merely to make up the numbers.

"Definitely I feel like my game's probably as good as it's ever been. My mindset is as good as it's ever been and hopefully I can get the breaks and come out on top," Leishman said from the US on Thursday.

LIV Golf superstar Bryson DeChambeau is the defending US Open champion and has routinely featured at the pointy end of the majors over the past two years.

Jon Rahm, Brooks Koepka, Patrick Reed and Phil Mickelson have also seriously contended at golf's four biggest annual events since switching to LIV, and Leishman strongly disagrees with the doubters, chiefly former pro turned analyst Brandel Chamblee, that the so-called "rebel" players can't win majors.

Leishman, who will also play this year's British Open at Royal Portrush following his Australian Open top-three finish in December, even believes LIV golfers enjoy some advantages at the majors.

"The way our schedule's set up actually lends itself to being able to prepare very well for the majors," said the six-time PGA Tour winner.

"We're playing against great fields every single week, on tough golf courses. Yes, it's 54 holes, but it puts a bit of pressure on that first round to get off to a good start because they are a little bit more of a sprint.

"We're still playing a lot of golf. Away from tournaments, enjoying golf more and, when you are enjoying your golf and it's not so much of a grind, that lends itself to better play.

"So, yeah, I'd probably disagree with Brandel Chamblee a little bit - a lot."

Great mate Cameron Smith has been accused of losing his competitive edge since joining LIV immediately after winning the 2022 British Open at St Andrews.

But, also rejecting the notion they have taken the money and run, Leishman also reckons the juices are still flowing for all the LIV players.

"I mean, we're all competitive," he said.

"A lot of people - the high-level athletes or actors or businessmen or business lady, whatever you want to say, just successful people - they already have the money in the bank and they just want to be successful.

"And they want to test themselves. I want to test myself against the best players, and we do that at the LIV events.

"Yes, there's no cuts and all that. But once you get into that end of the tournament and it's 'I win or you win', you're not even thinking about all that stuff.

"You know, you want to get yourself into that pressure cooker, if you call it that, and test yourself under the most immense pressure and see if you can handle it.

"That's why whether I'm playing the Victorian PGA or the LIV Miami or the US Open, I want to try to win."