William "Billy" Baldwin says President Donald Trump made sexual advances on Baldwin's wife at a hotel party in New York.

The actor made the accusations on Twitter after the president's son, Donald Trump Jr., tweeted about sexual harassment allegations against Senator Al Franken (D-Minn).

"Your Dad is a 5th degree black belt when it comes to sexual impropriety allegations," Baldwin tweeted in response. "In fact...I once had a party at the Plaza Hotel... your father showed up uninvited & hit on my wife... invited her on his helicopter to Atlantic City."

"She showed his fat a-- the door," the 54-year-old actor added.

According to the New York Daily News, a witness says Baldwin was hosting an intimate party at a Plaza hotel room for his soon-to-be-wife Chynna Phillips' birthday in the early 1990s. Trump, who owned the Manhattan hotel at the time, suddenly showed up and tried to get her to leave with him.

"He tried to coerce her into getting in his helicopter," the witness told the publication. "(Phillips) laughed uncomfortably at the prospect and said thanks but no thanks."

Billy Baldwin says Trump hit on his wife at Manhattan hotel - NY Daily News https://t.co/IUUiI2Br0w — SNOWFLAKE (@jawja100) November 24, 2017

Baldwin, known for his fellow acting brothers and roles in "Backdraft" and "Dirty Sexy Money," married the Wilson Phillips singer in 1995. They have three children together.

President Trump was married to Ivana Trump from 1977 to 1992, Marla Maples from 1993 to 1999. He married his third wife, First Lady Melania Trump, in 2005.

Trump, known as a reality TV star and business mogul before becoming president last year, has been accused of sexual harassment and assault by more than a dozen women. Last year, allegations re-emerged when a 2005 "Access Hollywood" tape leaked where he bragged to TV host Billy Bush about allegedly grabbing women by their genitals.

"I don't even wait. And when you're a star, they let you do it, you can do anything," Trump said.

Trump has denied all allegations of sexual misconduct.

Earlier this week, he encouraged Alabama voters not to vote for Democrat Doug Jones in a special election to fill the Senate seat once held by Attorney General Jeff Sessions. Jones' opponent, Republican candidate Roy Moore, is accused of sexual contact with two girls, including a 14-year-old, and romantic relationships with teenagers when he was a deputy district attorney in his 30s.

"Roy Moore denies it, that's all I can say," Trump said repeatedly Tuesday.

Last week, Trump blasted Franken for allegedly groping several women, including model and news host Leeann Tweeden.

"The Al Frankenstien picture is really bad, speaks a thousand words," Trump tweeted. "And to think that just last week he was lecturing anyone who would listen about sexual harassment and respect for women. Lesley Stahl tape?"

Trump has not commented on the claims by Baldwin. The actor's brother Stephen is an outspoken Trump supporter and former "Celebrity Apprentice" contestant," while Alec Baldwin has repeatedly criticized the president and mocked him in "SNL" skits.