Republican presidential candidate Donald Trump told a rally in Las Vegas on Sunday that he would seek to end taxation of income from tips, a direct appeal to service workers in the swing state of Nevada, which polls suggest is leaning his way ahead of the November 5 election.

Trump also once again talked up his supporters convicted for their roles in the January 6, 2021 attack on the US Capitol, calling them "warriors" and suggesting a possible counter-investigation into the event if he were re-elected.

The pledge on tips, revealed at a sweltering outdoor rally in Las Vegas where temperatures reached 37 degrees Celsius, adds one more detail to a Trump tax plan that has included vague pledges of tax relief to middle-income workers and small businesses.

"So this is the first time I've said this, and for those hotel workers and people that get tips you're going to be very happy because when I get to office, we are going to not charge taxes on tips people (are) making," Trump told a crowd of several thousand people.

Trump said he would "do that right away, first thing in office," and noted in prepared remarks that he would seek legislation in Congress to make the change. "You do a great job of service, you take care of people and I think it's going to be something that really is deserved."

Trump has previously pledged to make permanent the Republican-passed individual tax cuts that he signed into law in 2017 but which expire at the end of 2025. Tax experts estimate that doing so would raise US deficits by some US$4 trillion over a decade compared to current forecasts.

As current law requires, tipped employees must report their tips as income. Eliminating this would add further to deficits without new revenues elsewhere.

Trump's Democratic opponent, President Joe Biden, has pledged to maintain Trump's tax cuts for households earning under US$400,000 a year, but wants to substantially raise taxes on the wealthiest Americans and on large corporations.

The Las Vegas speech was Trump's first large-scale rally since a New York jury found him guilty on May 30 of falsifying documents to cover up a payment to a porn star on the eve of the 2016 election, making him the first former US president convicted of a crime. (Reuters)