Congressional Democratic leaders commended Biden's announcement outlining his COVID-19 emergency relief proposal.

"The emergency relief framework announced by the incoming Biden-Harris Administration tonight is the right approach. It shows that Democrats will finally have a partner at the White House that understands the need to take swift action to address the needs of struggling communities," House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer said in a statement.

"We will get right to work to turn President-elect Biden's vision into legislation that will pass both chambers and be signed into law," they added.

"The robust package announced by President-elect Biden and Vice President-elect Harris shows we now have the necessary leadership in the Executive Branch to turn this around and we are ready to get to work to deliver aid without delay," Pelosi and Schumer said.

-ABC News' Mariam Khan

Biden will propose a $1.9 trillion, “American Rescue Plan" to address the ongoing COVID-19 vaccination effort and immediate economic need to Americans in evening remarks, transition officials disclosed on a call with reporters Thursday.

According to officials on the call, the rescue policy is only one part of Biden’s overall policy, with a “recovery” phase expected to be introduced in February. They said Biden’s rescue policy will include three components: Tackling vaccine distribution, ramping up testing and getting kids back in school within the first 100 days of his administration; delivering $1,400 per-person direct stimulus checks and expanding unemployment benefits, including $400 weekly benefit through September on top of state benefits; and delivering aid to states and communities to support small businesses, addressing housing insecurity by expanding the eviction and foreclosure moratorium through Sept. 2021.

More than $1 trillion of the $1.9 trillion price tag will be used for direct stimulus, officials said, while $400 billion will go toward COVID-19-related projects, including the nationwide vaccination program, and $440 billion will go toward relief for communities and businesses.

Biden will also call for Congress to provide $350 billion for state local and territorial governments, an effort to keep essential workers on the job.

If enacted, it would be one of the largest and most expensive economic stimulus packages in U.S. history.

-ABC News Molly Nagle, John Verhovek, Beatrice Peterson and Averi Harper

Ahead of Biden's inauguration and in the wake of last week's attack at the Capitol, the United States Capitol Police (USPS) has enhanced security measures across the Capitol Complex, including adding fencing and making several street closures until further notice, the agency announced Thursday.

"Be advised that the U.S. Capitol Complex is closed to the public, and the Capitol Grounds will not be accessible to the public on January 20, 2021.  Anyone attempting to unlawfully gain access to the Capitol Grounds by climbing a fence or any other unlawful means will be subject to an appropriate use of force and arrest," the USPS said in a statement.

Workers were seen installing barbed wire on security fencing surrounding the Capitol on Thursday afternoon as National Guard troops, some armed, patrolled the area. As National Guard troops continue flowing into the area, there are currently over 7,000 currently stationed in Washington with that number expected to grow to 20,000 over the weekend.

-ABC News' Jake Date and Luis Martinez

House Minority Leader Kevin McCarthy, R-Calif., does not support efforts to remove Rep. Liz Cheney, R-Wyo, as House GOP conference chair and a member of House GOP leadership, a McCarthy spokesman told ABC News. This comes after some conservative House Republicans called on her to step down following her announcement that she supported impeaching Trump.

The Wyoming Republican and daughter of former Vice President Dick Cheney is the highest-ranking woman in Republican leadership and was reelected to by GOP members at the start of this Congress.

"We ought to have a second vote," Rep. Jim Jordan, R-Ohio, told reporters Wednesday about the leadership position. "The conference ought to vote on that."

"She should not be serving this conference," Rep. Andy Biggs, R-Arizona, said Tuesday.

On Wednesday night she joined nine other House Republicans in breaking from the party and voting to impeach Trump for his role in last week's riot at the Capitol.

-ABC News' Benjamin Siegel

Addressing the coronavirus pandemic, confronting the climate crisis and building public trust in science and technology will be among the Biden administration's key areas of focus, the president-elect said during a press briefing introducing four key members of his science team.

Building back the economy "to ensure prosperity is fully shared all across America" and ensuring the U.S. "leads the world in technologies and industries that the future" will also be a focus, Biden said Saturday during an address in Wilmington, Delaware.

Helping lead those initiatives will be Eric Lander, the presidential science advisor-designate, a position that for the first time will be a cabinet rank, Biden noted.

"I've always said that the Biden-Harris administration will lead with science and truth," Biden said. "We believe in both. This is how we're going to, God willing, overcome the pandemic and build our country back better than it was before. That's why for the first time in history, I'm going to be elevating the presidential science advisor to a Cabinet rank, because we think it's that important."

Frances Arnold and Maria Zuber will be at the helm of the first all-women team to lead the President’s Council of Advisors on Science and Technology.

Alondra Nelson will also be deputy director for science and society for the Office of Science and Technology Policy.

Dr. Francis Collins, who was not present at the event, will also continue in his role as director of the National Institutes of Health.Biden thanked him for "being willing to stay on," saying that it wasn't his original plan.

"I've known Dr. Collins for many years. I worked with him closely," Biden said, accling him "brilliant, a pioneer, a true leader."

"This is the most exciting announcement that I have gotten to make in the entire Cabinet," Biden said of his picks. "These are among the brightest, most dedicated people, not only in the country but the world."