WASHINGTON — Dirty details from Donald Trump’s messy divorce from his first wife, Ivana, are fair game, the mogul said Sunday, while warning Hillary Clinton he’ll ramp up attacks on Bill Clinton’s sex life if she labels the GOP front-runner a sexist.

“I don’t want to say it’s a threat, but it is a threat,” Trump said on NBC’s “Meet the Press.”

Reminded of the nasty details of his first divorce, the mogul said “it’s fine” for others to bring it up — but it’s a different circumstance than the Clintons.

“I wasn’t president of the United States. And I wasn’t dealing in the Oval Office,” Trump said.