Las Vegas casino billionaire Steve Wynn stepped down Saturday as Republican National Committee finance chairman, following allegations of decades of sexual misconduct.

The 76-year-old former business rival turned political ally of President Donald Trump had assumed the RNC position after Trump took office in January 2017.

Wynn has denied the allegations, first published in The Wall Street Journal on Friday, and accused his ex-wife Elaine of instigating the accusations as part of a "terrible and nasty lawsuit" seeking a revised divorce settlement.

"Today I accepted Steve Wynn's resignation as Republican National Committee Finance Chair," RNC chair Ronna Romney McDaniel said in a statement to AFP on Saturday.

Politico said McDaniel had discussed Wynn's case with Trump early Saturday. The president returned from the World Economic Forum in Davos, Switzerland, late Friday.

A towering figure in the gambling world, Wynn has been a prolific Republican donor whose empire includes casinos in Macau.