Donald Trump threatens to stop fundraising in face of opposition from Republicans

"Now, you have a couple of guys that were badly defeated and they're trying to organise maybe like a little bit of a delegate revolt," he said. "I thought they already tried that."

He condemned such efforts several times during his speech, claiming they were "illegal" and then dismissing them as a media-generated fabrication.

"It's all made up by the press," he said. "It's a hoax, I'm telling you."

While Mr Trump dismisses the effort as invented, more Republicans in Congress are saying they will not attend the party convention and are not endorsing his candidacy.

Meanwhile, a movement exists among some conservative delegates to change party rules to allow a different nominee, although it's a long shot effort lacking sufficient backing and a candidate to offer as an alternative.

Mr Trump wondered aloud who his opponents would pick as a replacement, a problem that has plagued the "Never Trump" movement for months.

"Who are they going to pick? I beat everybody. But I don't mean beat - I beat the hell out of them," he said.

Mr Trump has continued to face resistance from Republicans who have voiced increasing concern over his inflammatory rhetoric, and he appeared increasingly frustrated here, saying: "It would be helpful if the Republicans could help us a little bit."

The billionaire businessman also threatened that, if Republicans do not come together, he is prepared to stop fundraising and go back to largely self-funding his campaign.

"I'd love to do it," said Mr Trump, who has been holding fundraisers across the county this week largely benefiting the Republican National Committee. "You know, life is like a two-way street."

The event drew several thousand people, but many seats remained empty when he began speaking because of security screening delays. Even after he took the stage, the line of supporters circled the slot machines on the casino floor. Tourists carrying beer and wearing bikinis watched the crowds with amusement.

Mr Trump mistakenly blamed the delays on the Transportation Security Administration, which sometimes handles audience screening but was not involved in screening at Treasure Island.

Casino security, metro police and the Secret Service were handling those efforts at the Las Vegas event.

"I'm not happy about it, but I have to put up with it," he told supporters after erroneously blaming the TSA. "They didn't bring enough machines."

In a late afternoon rally in Phoenix, where temperatures reached 42C, the media-minded real estate developer bragged about the number of magazines that have placed him on their covers in recent months. "I feel like a supermodel, except like times 10," he said. "I'm a supermodel."

He also stepped up his criticism of President Barack Obama after the Orlando nightclub shooting. In Las Vegas, he told supporters: "If you think Orlando was the end of it with this weak attitude and this pathetic president we have, it wasn't, folks.

"You are going to have problems the likes of which you've never seen unless Donald Trump becomes your president."