Biden has officially reversed a ban on transgender people from serving in the U.S. military, signing an executive order in a brief ceremony in the Oval Office with Defense Secretary Lloyd Austin and Joint Chiefs Chairman Mark Milly looking on.

"What I'm doing is enabling all qualified Americans to serve their country in uniform," he said.

The White House had announced earlier he had done so in a release.

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

-ABC News' John Verhovek

Clarification: This story has been updated to reflect that the White House press release was issued before the actual signing.

As Biden assumes his first full week in office, he enters with only two Senate confirmed appointees -- lagging behind previous administrations in having Cabinet nominees confirmed.

The Senate convenes at 3 p.m. on Monday and will continue considering the nomination of Janet Yellen to be treasury secretary ahead of an evening vote.

After that, House impeachment managers will walk over and read the article of impeachment against former President Donald Trump to the Senate. The trial isn't slated to start until Feb. 8 to give Trump's defense time to prepare and Biden the chance to have his nominees confirmed and spending priorities addressed in the Senate.

On the campaign trail, Biden guaranteed his White House would "look like the country." Half of Biden's Cabinet picks are women, and the majority are people of color. Biden has noted that many of his selections would be pioneers in their roles -- including the first woman to serve as treasury secretary, the first Black defense secretary, the first openly gay man confirmed to a Cabinet role and the first Native American Cabinet secretary.

Last week, Avril Haines was confirmed as the first female Director of National Intelligence and Lloyd Austin as the first Black Pentagon chief.

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

That was the controversial ban put in place by former President Donald Trump in 2017 that reversed the Obama administration’s policy to allow open service by transgender people.

Newly-confirmed Defense Secretary Lloyd Austin -- the first Black Pentagon chief -- will be on hand at the White House ceremony Monday where the executive order will be signed.

Biden’s public schedule also includes an afternoon signing of an executive order related to American manufacturing and American workers -- fulfilling a long-time campaign promise to increase the amount of federal spending that goes to American companies. White House press secretary Jen Psaki is also scheduled to brief reporters at 1 p.m.

-ABC News' Luis Martinez

House impeachment managers are expected to deliver the article of impeachment for "incitement of insurrection" against former President Donald Trump to the Senate on Monday evening -- triggering the first impeachment trial of a former president that is slated to begin the week of Feb. 8 -- giving Biden a two-week window to work on his priorities.

Entering his first full week as president, Biden now gets to work on a sweeping and expensive legislative agenda where the crises are vast and the solutions are complex. An administration official said the president’s conversations with a bipartisan group of lawmakers over the weekend was “constructive,” but already he is coming up against the limits of the inaugural themes that earned him bipartisan praise.

Republicans like Sen. Mitt Romney who have warmed to Biden’s themes are balking at his price tags. And members of Congress who might be less sincere in their desire to work with the new White House are finding reasons to complain about the fast executive actions issued by the president.

The latest ABC News/Ipsos poll found hints of a Biden honeymoon, with broad and even somewhat bipartisan support for his handling of COVID-19 and for his aspirations to turn down the temperature on political rhetoric.

But when it comes to policy areas, such support starts breaking down. That includes overwhelming Republican opposition to Biden’s early moves on immigration and the border wall -- signature issues of former President Donald Trump that continue to bring out sharp partisan passions.

-ABC News' Political Director Rick Klein