As both a transgender person and a longtime Republican, Caitlyn Jenner felt compelled to speak out on the Trump administration’s decision Wednesday to revoke federal guidelines specifying that transgender students had the right to use public school restrooms that matched their gender identity.

In a video posted to social media Thursday, the former Olympic decathlon champion spoke directly to the president, reminding him that he “made a promise to protect the LGBTQ community” and telling him his policy “is a disaster.” She also referenced Trump’s attorney general, Jeff Sessions, while talking about “bullies,” who she described as “sick” and “weak.”

“I have a message for President Trump, from one Republican to another,” Jenner said. “This is a disaster. And you can still fix it. You made a promise to protect the LGBTQ community. Call me.”

While on the campaign trail in April, Trump made an appearance on the “Today” show and was asked about the so-called “bathroom bill” that North Carolina had recently enacted. Saying that the state was “paying a big price, and there’s a lot of problems,” he claimed, “There have been very few complaints the way it is.” When asked if Jenner “could use any bathroom she chooses” at Trump Tower, Trump said, “That is correct.”

As The Post’s Philip Bump pointed out, Trump’s subsequent pronouncements about doing “everything in [his] power to protect our LGBTQ citizens,” including at the Republican convention, were usually framed in the context of threats to those people from Islamist terrorists. Still, Jenner described Trump last summer as having “backed the LGBT community.”

Jenner, who won gold at the 1976 Games in Montreal, offered a different take Thursday but still tried to project a positive outlook. “I have a message for the trans kids of America: You’re winning,” she said in her video. “I know it doesn’t feel like it today or every day, but you’re winning. Very soon, we will win full freedom nationwide and it’s going to be with bipartisan support.”

She then moved to “a message for the bullies.” Jenner said, “You’re sick. And because you’re weak, you pick on kids, you pick on women or anyone else you think is vulnerable. Apparently even becoming the attorney general isn’t enough to cure some people of their insecurities.”

Referencing a transgender teen, Gavin Grimm, who sued his school board for barring him from the boys’ bathroom, Jenner said, “Mr. President, we’ll see you in court.”

Formerly known as Bruce Jenner, she revealed her transition from male to female in April 2015. Thanks to her ongoing appearances in the long-running reality show “Keeping Up with the Kardashians,” as well as her athletic fame, Jenner has become a prominent advocate for the LGBT community.