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."

More than 21,500 National Guardsmen are currently in Washington, the D.C. Guard confirmed to ABC News on Monday.

The security preparations come ahead of Biden’s inauguration and in the aftermath of the deadly Capitol raid conducted by Trump supporters earlier this month. 

The ramp-up in the number of guardsmen in the nation's capital means there could be four times as many American military service members in the city than there are in Iraq and Afghanistan combined.

The guardsmen are working in shifts to provide round-the-clock security both inside the Capitol and around the perimeter of the Capitol grounds. 

-ABC News’ Luis Martinez