Trump put the ban in place that did not allow transgender people to serve.

Multiple people familiar with the matter confirm to ABC News that President Joe Biden is expected to sign an executive order on Monday that will lift the Pentagon’s ban on transgender people serving in the military.

The controversial ban was announced by former President Donald Trump in 2017 through a tweet and reversed the Obama administration’s policy to allow open service by transgender people.

New Defense Secretary Lloyd Austin will be on hand at the White House ceremony on Monday, where the executive order will be signed, said the individuals familiar with the matter.

“The ban will be officially lifted tomorrow,” said one of the individuals familiar with the signing of the executive order.

Biden had said during the presidential campaign that he favored repealing the ban.

In May 2020, Biden had said he would direct the Pentagon to let “transgender service members serve openly and free from discrimination in the military.”

“They can shoot as straight as anybody else can shoot,” he added.

At his confirmation hearing last week Austin had said he would support an effort to repeal the ban.

“I support the president’s plan to overturn the ban,” Austin told the Senate Armed Services Committee. “If you’re fit and you’re qualified to serve and you can maintain the standards, you should be allowed to serve, and you can expect that I will support that throughout.”

The White House and the Pentagon declined to comment on the executive order.

It is unclear how many transgender people serve in the military, though some advocacy groups have said it could be as high as 15,000 individuals.

In 2016, Defense Secretary Ash Carter announced a policy that would allow transgender individuals to serve in the U.S. military openly.

But in July 2017, Trump issued a series of tweets that immediately banned such service.

The tweets blindsided Pentagon officials, including James Mattis, Trump’s first defense secretary.

He soon implemented reviews that led the Pentagon to re-institute a ban on open transgender service two years later.

The new policy required service members and those wishing to join the military to adhere to the standards associated with their biological sex.

Service members diagnosed with gender dysphoria, defined as “a marked incongruence between one’s experienced/expressed gender and assigned gender … associated with clinically significant distress and impairment of functioning,” were no longer allowed to receive medical surgeries for gender transition unless they were currently in the process of receiving medical treatment.

Transgender individuals who had received hormones or medical surgery related to their transition were barred from joining the military, even if they could prove stability in their preferred gender.

ABC News’ Molly Nagle and Elizabeth McLaughlin contributed to this report.

This report was featured in the Monday, Jan. 25, 2020, episode of “Start Here,” ABC News’ daily news podcast.

“Start Here” offers a straightforward look at the day’s top stories in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, Spotify, the ABC News app or wherever you get your podcasts.