President-elect Donald Trump’s newly picked “border czar” Tom Homan addressed his forthcoming deportation plan and state leaders who have objected to sweeping immigration policies.

During an appearance on Fox News on Monday, Homan issued a warning to so-called “sanctuary” states and cities to “get the hell out of the way” of the Trump administration's mass deportation plans.

“I saw today numerous governors from sanctuary states saying they're going to step in the way. They better get the hell out of the way. Either you help us or get the hell out of the way, because ICE is going to do their job,” he warned, referring to the U.S. Immigration and Customs Enforcement, where he formerly served as director.

"I'll double the workforce in that sanctuary city. We're going to do our job despite the politics. We're doing it. So get used to it, because we're coming,” Homan said.

When asked if he plans to deport American citizens, Homan said, “President Trump has made it clear we will prioritize public safety threats and national security threats first, and that's how the focus would be.”

-ABC News' Soo Rin Kim

President-elect Donald Trump is expected to announce his intention to nominate Sen. Marco Rubio (R-Fla.) for secretary of state, according to multiple sources familiar with the matter.

Rubio, 53, has served in the Senate since 2011. He is currently the vice chair of the Senate Select Committee on Foreign Intelligence, and he also sits on the chamber’s Foreign Relations Committee.

Several long-serving State Department officials tell ABC News they respect Rubio’s extensive foreign policy experience and view him as unlikely to overly politicize the secretary of state role.

The secretary of state is appointed by the president with the consent of the Senate.

-ABC News' Katherine Faulders and Shannon Kingston

Trump has asked Rep. Mike Waltz, R-Fla., to be his national security adviser, multiple sources said.

Waltz was at Mar-a-Lago on Monday, sources said.

The national security adviser is appointed by the president without confirmation by the Senate.

Waltz is a former Green Beret and China hawk who emerged as a key surrogate for Trump, criticizing the Biden-Harris foreign policy record during the campaign.

The Florida Republican sits on the Intelligence, Armed Services and Foreign Affairs committees.

He has supported aid to Ukraine in the past but has demanded "conditions," including increased spending from European allies, additional oversight of funds and pairing the aid with border security measures.

Waltz, who has visited Ukraine, was a vocal critic of the Biden administration's policy towards Ukraine, criticizing the White House and allies for not providing Ukraine with more lethal aid -- such as MiG fighter planes -- earlier in the conflict.

Before running for elected office, Waltz served in various national security policy roles in the Bush administration, Pentagon and White House.

Trump had four different national security advisers during his first term, outside of those who served very briefly: Michael Flynn, H.R. McMaster, John Bolton and Robert O’Brien.

-ABC News' Rachel Scott, Benjamin Siegel, John Santucci and Katherine Faulders

A volunteer-run effort on Robert F. Kennedy Jr.'s website has begun crowd-sourcing ideas for appointments in Trump's administration.

A website titled "Nominees for the People" gives anyone the chance to submit names of people they'd like to see join the administration.

"President Trump and Robert F. Kennedy Jr. want your help nominating people of integrity and courage for over 4,000 appointments across the future Trump administration," the website reads.

Stefanie Spear, a Kennedy spokeswoman, told ABC News that the crowd-sourcing effort is "a grassroots initiative run by volunteers," and is not actually spearheaded by Kennedy, although the page uses the "mahanow.org" URL that Kennedy's official campaign website adopted after he exited the race.

"We’ve always offered space on our website to our grassroots movement," Spear said.

This post has been updated to reflect that the crowd-sourcing effort is a volunteer-run effort.

-ABC News' Sasha Pezenik