Las Vegas, Nevada - Thousands of Donald Trump supporters rallied in baking heat Sunday to cheer on the Republican presidential candidate in Nevada, a key battleground state in November's election.

"It's not too hot out here, right?" the 77-year-old told a cheering crowd in Las Vegas.

"If you start going down, we have people. They'll pick you up right away. They'll throw water."

The gathering in Sunset Park was Trump's first major rally since he was found guilty late last month of falsifying business records to hide a hush money payment to porn star Stormy Daniels shortly before the 2016 presidential election.

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But for his most loyal followers, the verdict only strengthened Trump's position against his Democratic rival, President Joe Biden.

"I don't care about what happened to him in the trial... it doesn't change my mind about him at all," Lindsay Elliott, who came to the Trump event with her family, told AFP.

"I think it's going to help him. I think that the American people are done with this crap," the 40-year-old added.

Her daughter Mackenzie (19) agreed: "It sucks what happened but I think it's just going to make him stronger and make voters more encouraged to vote (for him)."

Trump, who faces three other criminal cases which are unlikely to be heard before the November election, spoke for just under an hour and attacked Biden as "the worst president in the history of our country."

The Republican repeated conspiracy theories that the 2020 election was "stolen" by Democrats – despite exhaustive investigations finding no such evidence, and him being charged in relation to his alleged attempts to overturn the ballot result.

Trump also spoke ominously of the consequences if he is not elected in November, telling supporters: "If it doesn't happen, you're headed to World War III."

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He also promised to end taxation of tips for service workers.

By 10:00 AM Sunday in Las Vegas, as the thermometer already read 93 degrees Fahrenheit amid a heatwave, people wearing the traditional red of the Republican Party were queuing to hear Trump speak at midday, when the mercury soared to triple digits.

Vendors sold t-shirts reading "I'm voting for the convicted felon" along the mile-long line.

Near the end of the rally, at least one person overcome by the heat was seen being attended to by paramedics.