Trump transition live updates: Sen. Marco Rubio eyed for secretary of state: Sources

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 and criticized the Biden-Harris foreign policy record during the campaign.

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

He has previously supported aid to Ukraine but has demanded “conditions”, including increased spending by 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 toward Ukraine, criticizing the White House and allies for not providing Ukraine with more lethal aid — such as MiG fighter jets — earlier in the conflict.

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

Trump had four different national security advisers in his first term, in addition to those who served very briefly: Michael Flynn, HR McMaster, John Bolton and Robert O’Brien.

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