A spokesperson for the U.S. Army confirmed that there will be 25,000 National Guardsmen in the nation’s capital to aid with security for Biden’s inauguration.

“The Defense Department has agreed to provide up to 25,000 service members to support the Presidential Inauguration National Special Security Event federal law enforcement mission and security preparations, as led by the U.S. Secret Service,” the spokesperson said. “The Department of the Army and the National Guard Bureau are working on a sourcing solution now to support this request.”

-ABC News’ Luis Martinez

The FBI, DHS, Secret Service and U.S. Capitol Police, along with several local law enforcement agencies, have issued an extensive "threat assessment" surrounding Wednesday's inauguration.

It covers a range of threats surrounding the inauguration, including not only physical threats from domestic terrorists but also influence campaigns from Russia, China and Iran stemming from the Capitol siege. It even covers physical threats from drones.

The memo says domestic extremists is the “most likely” threat to the inauguration, citing recent incidents of ideologically motivated violence, including the deadly mob at the U.S. Capitol building.

Regarding foreign concerns, the assessment said that since the incident at the Capitol, “Russian, Iranian, and Chinese influence actors have seized the opportunity to amplify narratives in furtherance of their policy interest amid the presidential transition.”

“We have not identified any specific, credible information indicating that these actors intend to explicitly commit violence,” it added. “Furthermore, we have not identified any specific, credible cyber threat to critical infrastructure supporting the upcoming Presidential Inauguration nor a specific credible cyber threat to military or law enforcement personnel supporting the event."

The memo did say, however, that Russian state media has “amplified themes related to the violent and chaotic nature of the Capitol Hill incident, impeachment of President Trump, and social media censorship.”

Iranian state media has “continued to stoke claims that President Trump encouraged and incited the violence, as well as calls to invoke the 25th amendment,” the memo added. It has also “amplified perceived concerns related to President Trump’s mental health and the prospect of other risky actions he could take before leaving office.”

Finally, it noted that Chinese media has “seized the story to denigrate US democratic governance -- casting the United States as broadly in decline -- and to justify China’s crackdown on protestors in Hong Kong."

Lastly, the memo warned that drones could disrupt law enforcement operations at the inauguration, though it added that it does not have “specific, credible information” indicating malicious actors have plans to use unmanned aircraft systems to target the event.

-ABC News’ Mike Levine

Vice President Mike Pence spoke with Vice President-elect Kamala Harris on a call Thursday, sources familiar with the call told ABC News.

The news was first reported by the New York Times.

-ABC News’ Molly Nagle, Justin Gomez and Katherine Faulders

Sources told ABC News that Trump has requested a large sendoff hours before President-elect Biden takes the oath of office Wednesday.

Sources say Trump plans to depart the White House next Wednesday morning, choppering via Marine One to Joint Base Andrews where he is expected to give remarks to supporters and departing members of his administration.

Sources add that Trump has requested the event to have a "military-like feel" though details are still not finalized. The president will then fly down to his Mar-a-Lago club in Florida onboard Air Force One with a small number of staffers who will be part of his post-presidency operation, according to the sources.

-ABC News’ John Santucci and Katherine Faulders

Eric Lander is Biden's nominee for presidential science adviser, a position Biden announced Saturday he is elevating to a Cabinet-level position for the first time in U.S. history.

Lander served as the co-chair of the President’s Council of Advisors on Science and Technology (PCAST) during the Obama-Biden administration. He currently serves as president and the founding director of the Broad Institute of MIT and Harvard. Landon is also one of the principal leaders of the Human Genome Project.

"It's not hyperbole to suggest that Dr. Lander's work has changed the course of human history. His role in helping us map the genome, pull back the curtain on human disease, allowing scientists ever since and for generations to come to explore the molecular basis for some of the most devastating illnesses affecting our world," Biden said.

In his remarks Saturday, Lander said, "The President-Elect knows that science and technology will be crucial in meeting this moment," adding that "America's greatest asset, I think, is our unrivaled diversity. After all, scientific progress is about seeing something that no one’s ever seen before. Because they bring a different lens, different experiences, different questions, different passions. No one can top America in that regard. But we have to ensure that everyone not only has a seat at the table, but a place at the lab bench."