Donald Trump has warned Republican elites that his supporters know they are being 'disenfranchised' through the 'crooked shenanigans' of the GOP's delegate selection process.

'You know what? They're taking your vote away. They're disenfranchising people,' he said in between chants of 'USA!', 'we want Trump!' and 'build that wall!' among 10,000 fnas crammed into a private aviation hangar in Rochester, New York.

'I say this to the RNC and I say it to the Republican Party: You're going to have a big problem, folks, because the people don't like what's going on, Trump warned.

Trump had previously forecast 'riots' among the GOP's rank and file if he won more elected primary delegates than any other Republican candidate but were still denied the nomination.

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FIRING BACK: Donald Trump warned the GOP not to monkey with the delegate process on Sunday, saying it's unfair when he wins the popular vote in some states but trails there in delegate counts

'CROOKED SHENANIGANS': Trump pointed the finger at the Republican National Committee

'What we have going is a movement,' he said.

'Now, they're trying to subvert the movement. They can't do it with bodies. They can't do it with people because they don't have near the people that we have. So what they're trying to do is subvert the movement with crooked shenanigans. And we're just not going to let it happen.'

Trump said he 'should win' the Republican presidential nomination outright 'before we get to the convention' in July.

But on the heels of a series of statewide victories by his rival Ted Cruz that were the result of political arm-twisting, not ballot-casting, Trump appeared to be running out of patience.

One such state, Louisiana, saw the billionaire win unexpectedly by more than three per cent last month. But because Cruz's staffers showed up to take part in the Republican Party's post-election procedural wrangling, the Texas senator may go to the convention with more of the state's delegates than Trump.

'We've got a corrupt system,' Trump told supporters on Sunday.

'It's not right. We're supposed to be a democracy. We're supposed to be: You vote and the vote means something, all right? You vote, and the vote means something. And we've got to do something about it.'

'We should have won a long time ago but we keep losing where we're winning. Today winning votes doesn't mean anything,' he said.

'LYIN' TED' CRUZ: The Texas senator has become Trump's main foil as his staff works to outmaneuver Trump's for delegates not appointed in popular-vote elections

DEVOTED: A 10,000-strong crowd of people crammed into a private aviation hangar in Rochester, New York, for Trump's speech

'I win Louisiana ... then I find out that I get less delegates than Cruz because of some nonsense going on?'

'We've got to have a system where voting means something,' he said later. 'Doesn't voting mean something?'

But the real estate tycoon put a brave face on his back-room losses, insisting that 'I think we're going to be fine. We're doing really well'.

He also expressed some unusual solidarity with Vermont Sen. Bernie Sanders, the far-left democratic socialist who has provided Hillary Clinton's only competition in the Democratic Party primary process.

Despite a run of eight primary and caucus wins in the last nine votes, Sanders is still trailing the former secretary of state – largely on the strength of 'superdelegates' - the party bosses and elected officials whose seat at their convention isn't decided by voters.

Clinton long ago sewed up the support of most of that group.

'In all fairness, take a look at what happens with Bernie,' Trump said. 'He wins, he wins, he wins, he wins, and I hear he doesn't have a chance. This is a crooked system, folks.'

While allowing that 'I'm not a fan of Bernie', Trump compared his own situation to that of Sanders.

'He wins, and he wins. Like me! I've won twice as much as Cruz,' Trump said. 'I've won millions and millions of votes more. People who have never voted are coming out to vote for Trump.

'Why doesn't he have a chance?' he asked, referring to Sanders. 'Because the system is corrupt. And it's worse on the Republican side. ... Whether it's me or whether it's Bernie Sanders, when I look at it and I see all these victories that I have, and all the victories that he's got ... it's a corrupt thing going on.'

Trump called on his followers to come out in droves for the New York primary on June 19.

'We need a great show of strength,' he said.

'You've gotta go out and you've gotta go vote en masse.'

BERNIE'S BFF? Trump said Sanders doesn't have a chance in the Democratic primary process for the same reason he's being sidelined in the Republican race: a 'corrupt' nominating system

WIND CHILL: Temperatures outside in Rochester were in the high 30s to low 40s as Trump spoke to about 10,000 people on Sunday

Trump is already polling at 54 per cent in the Empire State, according to a Fox News poll released Sunday. That is a political universe away from Ohio Governor John Kasich's 22 per cent.

Cruz, whose campaigning has been hapless in New York, is polling a distant third with just 15 per cent.

Trump made one bit of odd news on Sunday, saying one-time Republican gubernatorial candidate Carl Paladino had asked him to run for governor, but he declined because he knew he would be running for president this year.

'I sort of said, "I'm sorry, but I'm doing something else",' he recalled. 'I didn't want to say – this is what the something else was.'

The last such election in New York came in 2014, four years after Paladino lost to current governor Andrew Cuomo.

Trump left a trail of bread crumbs as a hint about his intentions even earlier, filing for trademark protection for his 'Make America Great Again' slogan less than two weeks after the 2012 election.

He said if he had run for governor, people in western New York 'would have been fracking by now', a reference to Cuomo's refusal to green-light new natural gas exploration.