Biden and Vice President-elect Kamala Harris are participating in a virtual briefing with expert members of their national security and foreign policy agency review teams from the Queen Theater in Wilmington, Delaware, and taking the opportunity to draw stark contrasts between Trump's "America First" policy and their incoming White House.

At the top of the briefing, Biden praised the team for their work despite delays in the transition prompted by the Trump administration refusing to recognize Biden's ascertainment as the president-elect for more than two weeks.

"You’ve done it all under incredibly difficult circumstances, dealing with the COVID protocols, delays, delays in the ascertainments, and in a few cases obstruction from the current leadership," Biden said, thanking the group before taking aim at Trump's "go-it-alone approach" of the past four years.

“The truth is, the challenges we face today can't be solved by any one country acting alone. They demand American leadership. They demand cooperation with our allies and our partners. So I’m looking forward to hearing your assessments about the greatest challenges we may inherit and as we restore the principle of American leadership on the global stage -- which we have to and will do," Biden added.

After the briefing, Biden is slated to deliver afternoon remarks on the group's findings.

-ABC News' Molly Nagle

Dr. Celine Gounder, a member of Biden’s COVID-19 task force, said Monday morning there is "no question" the country will see a post-holiday surge of coronavirus cases and, to help offset the worsening pandemic, confirmed Biden will invoke the Defense Production Act once in office to increase vaccine supply.

Gounder criticized the Trump administration for moving too slowly on vaccine distribution and said Biden will force manufacturers to step up by invoking the Defense Production Act, which gives the president the power to direct civilian businesses to help meet orders for products necessary for national defense.

“In the last two weeks, we basically averaged about a million doses of vaccine administered per week. We need to be getting to a million doses per day if we're going to reach the president-elect's target of 100 million doses in 100 days," Gounder said. She went on to explain that invoking the act is "to make sure that the personal protective equipment, the test capacity and the raw materials for the vaccines are produced in adequate supply so that those aren't limiting steps in all of this.”

Gounder also claimed the country will see "a major increase" in testing as well as in genetic surveillance to track new variants of the virus with the incoming administration.

-ABC News’ Brian Hartman

Trump is slated to return to Georgia in one week for a campaign rally on the eve of the Jan. 5 runoff races that are set to determine which party holds power in the U.S. Senate.

Sitting GOP Sens. Kelly Loeffler and David Perdue are facing off against Democratic contenders Rev. Raphael Warnock and Jon Ossoff, respectively, as early voting continues across the state Monday.

Earlier this month Trump stumped for Loeffler and Perdue at his first rally since the November election. There, he assaulted the integrity of Georgia's vote but encouraged GOP turnout in the wake of Biden becoming the first Democratic presidential candidate to win the state since 1992. Democrats are now hoping to cement its status as a swing state.

Biden, too, has stopped in Georgia since the presidential election to campaign for Warnock and Ossoff as the promise of passing the big ticket legislation he’s hoping for hangs on their races. If Democrats pick up both seats, Vice President-elect Kamala Harris will have the power to settle tie-breaker votes in Congress' upper chamber.

The Biden-Harris transition team has announced 12 new members of their incoming staff for the Office of Digital Strategy -- which the transition says will be a “robust” team in the Biden White House.

All 12 staffers announced Monday morning previously worked on the Biden-Harris campaign, which relied heavily on digital engagement amid the COVID-19 pandemic.

"With much of our lives online, it is critical for this administration’s digital efforts to be inclusive and extensive,” said Vice President-elect Kamala Harris in a joint statement announcing the picks.

-ABC News Molly Nagle

In a previously recorded campaign-style video posted to Twitter Thursday, President Donald Trump touted what he views as his many presidential accomplishments: producing COVID-19 vaccines, repairing the economy and stopping "endless foreign wars" in the Middle East.

When it comes to vaccines, Trump said, "Our most vulnerable citizens are already receiving the vaccine and millions of doses are quickly being shipped all across our country."
The president promised that "by early next year the vaccine will be available to every American."

The Trump administration had promised that 20 million people would be vaccinated by the end of the year. As of Wednesday morning, 2,794,588 Americans had received vaccine doses and 12.4 million doses had been distributed, according to the Centers for Disease Control and Prevention.

Trump also boasted about the economy, saying, "Through the Paycheck Protection Program, we saved or supported more than 51 million American jobs, and we're doing numbers now like nobody's ever seen before, including having the highest stock market in the history of the world."

"We have slashed the unemployment rate from 14.7%, all the way down to 6.7%," Trump said. "Our economy is growing at the most rapid rate ever recorded. ... Nobody can compete with us in terms of going down less, and going up by far the fastest and the best. Whenever America's challenged, we always rise to the occasion."

Many economists, however, have argued that the economy is rebounding in a K-shape, as opposed to a V-shape, with the rich getting richer and the working class still struggling.

The president also touched on foreign affairs.

"We have secured our borders and paused immigration to protect American workers," Trump said. "And after years of endless foreign wars we are signing historic peace deals in the Middle East. It's all ending in the Middle East. We have to hope it keeps going. It's so easy if you know what you're doing."

While Trump has successfully pushed to normalize relations between Israel and many Middle Eastern countries, it's not accurate to say they are "peace deals" and they have come at the expense of Palestinians and aligned the countries against Iran. Iran, and its nuclear ambitions, continues to be a thorn in America's side. Trump has drawn down forces from Afghanistan and Iraq, but promised negotiations between the Afghan government and the Taliban fell apart and ISIS and al-Qaida affiliates are taking advantage of the insecurity in Syria, Northern Africa and elsewhere.

ABC News' Elizabeth Thomas contributed to this report.