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

The controversial ban was put in place by former President Donald Trump in 2017 that 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 Monday, where the executive order will be signed. 

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

-ABC News' Luis Martinez

The 7,000 National Guard troops requested for post-inauguration assistance in Washington will draw down to 5,000 through mid-March, a National Guard bureau official told ABC News in a statement Sunday.

And while the current plan is to assist through mid-March, "the National Guard will stay as long as needed at the request of supporting agencies," the statement continued.

The troops will be offering security, communications, medevac and logistical support, according to the statement. 

-ABC News' Matt Seyler

Biden continued his weekly routine of attending mass and chose Holy Trinity Catholic Church in Georgetown as his place of worship for his first Sunday in office.

A pool report indicated that Biden's son Hunter, and two granddaughters, Maisey and Finnegan Biden attended mass with him. The presidential motorcade also stopped at a bagel shop. The president was not seen getting out, but a reporter was told Hunter Biden went inside to pick up food. The president and his family returned to the White House a few minutes later.

-ABC News' Molly Nagle

In his appearance on ABC's "This Week" Sunday, Biden’s nominee for Surgeon General Vivek Murthy said that when it comes to meeting the goal for 100 million vaccines in the first 100 days of the president's administration, there are things that could go right or wrong.

"I think President Biden fully understands there's a larger goal here, as we all do, which is that we've got to vaccinate as many Americans as possible. And that's going to take a lot of work, work dispelling this disinformation, working on the supply, increasing distribution channels," he told ABC News Chief Anchor George Stephanopoulos. "And that's some of what the vaccine plan that he announced over the last week is intended to -- to achieve."

Stephanopoulos pressed Murthy on whether there are ways to increase the supply and equitably distribute the vaccines.

"It appears, at least in these first vaccines that have gone out, they've been going largely to wealthier areas of the country, largely to whiter areas of the country," Stephanopoulos said.

"Well, it's the right question, George, because success has to be gauged not just by the number of vaccines we deliver but also by how fairly we deliver those vaccines -- how equitably we deliver them," he said in response. "What we've got to do here is not just, again, increase supply, which we can do using the Defense Production Act ... but we've also got to set up the kind of distribution channels, like mobile units, like strategically placed community vaccination centers, that can reach people who traditionally are hard to reach and don't have access to health care."

He added, "We have got to track our progress. We have got to make sure that we have data on where the vaccine is being administered, so that we can ensure that it, in fact, is being distributed equitably."

The United States will remain a member of the World Health Organization, Dr. Anthony Fauci, the nation's leading infectious disease expert, announced Thursday.

Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, made the announcement via video link to the WHO's executive board in Geneva, a day after Joe Biden was sworn-in as the 46th president of the U.S.

"I am honored to announce the United States will remain a member of the World Health Organization," Fauci told the board Thursday, adding that the U.S. will also "fulfil its financial obligations" to the WHO and stop reducing its staff at the United Nations agency.

Fauci, who is Biden's chief medical adviser on the coronavirus pandemic, also announced that the president will issue a directive Thursday that shows the country's intent to join the COVAX Facility, a global initiative to ensure rapid and equitable access to COVID-19 vaccines for all countries regardless of income.

Within hours of becoming president, Biden had signed an executive order reversing former President Donald Trump's decision to withdraw from the WHO. Trump had accused the organization of failing to correctly respond to the coronavirus pandemic and of allegedly giving too much power to China.

In an interview Thursday with ABC News' Michael Strahan on "Good Morning America," Fauci said rejoining the WHO is "very important" and that the country's withdrawal "was very disconcerting to everybody."

"When you're dealing with global pandemic, you have to have an international connectivity, and for us to not be in the WHO was very disconcerting to everybody, all the member countries including the health officials here in the United States," he said. "So the official announcement that we are rejoining, we're going to live up to our financial commitments and a whole bunch of other things, it was really a very good day. I mean, the response I'm getting from my colleagues all over the world is really very refreshing."

-ABC News' Morgan Winsor