Trump inauguration live updates: Donald Trump moves swiftly to implement his new agenda

The State Department is charging full steam ahead with preparations for Sen. Marco Rubio's first full day as America's top diplomat.

Assuming all goes to plan, two State Department officials say that Rubio -- Trump's nominee to be secretary of state -- will give a speech to mark his arrival on Tuesday. He will also meet both one-on-one and as a group with the foreign ministers of India, Australia, and Japan -- the three countries that, along with the U.S., make up the Quad, a diplomatic partnership seen as critical to countering China's influence in the Pacific.

The Senate is expected to begin working to formally install as many of Trump's nominees as possible and Rubio is expected to come up first. He could be confirmed as soon as this evening.

The flag at the White House has been raised after Trump signed a proclamation for flags to be flown at full staff on all inauguration days.

The flag had been at half-staff following President Jimmy Carter's death on Dec. 29. Trump is ordering the flag to return to half-staff on Tuesday for the remainder of the 30-day period, which began the day of 100-year-old Carter's death.

Last week, House Speaker Mike Johnson ordered that the flags at the Capitol be raised for the inauguration.

With a flurry of executive orders expected today, President Donald Trump's top advisers, including his incoming Department of Justice leadership, are preparing for a storm of legal challenges to some of the most controversial ones.

"We're going to get sued on all of these things," one top Trump adviser said, adding that the volume of litigation is expected to be a full-time job for Trump's DOJ.

Trump has privately told advisers that he believes flooding the zone with executive orders will lead to lawsuits that may be less effective given the volume of actions he plans to take.

During Trump's first administration, he faced upwards of 400 lawsuits challenging his actions. His advisers anticipate more than that this time.

There will be a team inside the Justice Department that is dedicated just to defending Trump's actions in court, sources said.

-ABC News' Katherine Faulders

The transition from the Biden White House to the Trump White House is well underway and crews are working quickly to make the changes before Trump arrives later this afternoon, but the choices are nearly identical to his first term.

In the Oval Office, gold curtains have returned behind the Resolute Desk, as well as the red-and-beige carpet with green leaves that covered the wood floor.

As Trump sits at his desk, the portrait of President Andrew Jackson returned to the wall on his left side, just as it was during his first term. Biden had a portrait of Benjamin Franklin.

To Trump's right, where Biden hung a 1917 flag-decorated Childe Hassam painting, President Abraham Lincoln is now back on display.

Other areas of the West Wing still need to be unboxed. In the Cabinet Room is a cardboard box with "DJT Office Bibles" written on the side.