WASHINGTON (NewsNation Now) — President-elect Joe Biden is building out his administration with several key picks for national security and foreign policy roles.

Biden is expected to formally introduce some of his nominees and appointees on Tuesday.

John Kerry, a former secretary of state, will lead the incoming administration’s effort to combat climate change.

Kerry posted a statement on Twitter that said: “America will soon have a government that treats the climate crisis as the urgent national security threat it is. I’m proud to partner with the President-elect, our allies, and the young leaders of the climate movement to take on this crisis as the President’s Climate Envoy.”

Alejandro Mayorkas will be nominated as secretary of the Department of Homeland Security. He tweeted after his nomination Monday: “When I was very young, the United States provided my family and me a place of refuge. Now, I have been nominated to be the DHS Secretary and oversee the protection of all Americans and those who flee persecution in search of a better life for themselves and their loved ones.”

Mayorka, a Cuban-American lawyer, will be the first Latino to lead Homeland Security.

Biden also plans to nominate Linda Thomas-Greenfield as the U.S. ambassador to the United Nations.

Thomas-Greenfield tweeted a statement: “My mother taught me to lead with the power of kindness and compassion to make the world a better place. I’ve carried that lesson with me throughout my career in Foreign Service – and, if confirmed, will do the same as Ambassador to the United Nations.”

Biden’s other picks include Antony Blinken as his secretary of state, Avril Haines as the director of national intelligence and Jake Sullivan as a national security advisor.

Sullivan, who at 43 will be one of the youngest national security advisers in history, was a top aide to former Secretary of State Hillary Clinton before becoming then-Vice President Biden’s national security adviser.

The posts to be held by Kerry, Sullivan and Haines do not require Senate confirmation.

Biden is also expected to nominate Janet Yellen, the former Federal Reserve chair, as treasury secretary, the first woman to hold that post. That’s according to a person familiar with Biden’s plans who spoke to The Associated Press on condition of anonymity to discuss them.

By naming some key cabinet members and appointment, mostly in the national security sphere, Biden signaled what his incoming administration’s priorities will be.

“President-elect Biden is trying to show the primacy that he’s going to give to national security matters,” said Glen Johnson, a senior advisor to then Secretary of State John Kerry. He says Biden’s choice to fill the Secretary of State role, Tony Blinken, sends a message to American allies.

“It’s going to be more of a return to classic, diplomatic engagement that Joe Biden has always believed in. That’s what Tony Blinken has practiced,” Johnson said.

A return to diplomatic engagement would be a contrast to President Trump’s America-first policy, which resisted international organizations and treaties. President Trump pulled the U.S. out of the World Health Organization, the Paris Climate Accords, the Iran Deal, and the Open Skies Treaty. President Trump also threatened to pull the U.S. out of NATO.

Johnson also says it’s helpful that many of Biden’s choices served in previous administrations. Most served in the Obama Administration.

“These positions are incredibly grueling, the challenges come at you on a 24/7 basis. It’s not a great time to have on the job training,” said Johnson.

Dr. Todd Belt, Director of the George Washington School of Political Management also says experience in previous administrations is key, and often brings well-established relationships with foreign leaders to a new administration.

Belt also says the diversity of the cabinet could be an asset internationally.

“It’s not going to be a bunch of old white guys talking to you. It may be some people who look like you, and the people where you’re from. That does lend some credibility,” said Belt.

In the most high-profile position outside of national security, Biden is expected to name Janet Yellen as his choice for Treasury Secretary. Yellen was the first woman to serve as Chairman of the Federal Reserve, and if confirmed will be the first woman to serve as Treasury Secretary.

Belt also says Biden’s naming John Kerry as Special Presidential Envoy for Climate raises the importance of the issue.

“That really elevates the topic in the administration…This is a key concern of the incoming president,” said Belt.

Belt said he’s surprised Biden hasn’t named a Republican to the cabinet yet, to earn some goodwill among Senate Republicans before they vote on Biden’s nominees. The President-Elect is reportedly considering Republicans to appoint to a lesser consequential position.

Some Republicans, including Senator Tom Cotton from Arkansas, took issue with Biden’s picks, saying in a tweet:

“As [former Defense Secretary] Bob Gates said, Joe Biden has “been wrong on nearly every major foreign policy and national security issue over the past four decades.”

Meanwhile, high-profile Democrats praised Biden’s choices. Speaker of the House Nancy Pelosi said they bring “A legacy of unmatched diplomatic achievements to the critical mission of keeping the American people safe.”

The stakes of a smooth transition are especially high this year because Biden will take office amid the worst pandemic in more than a century, which will likely require a full government response to contain.

Biden has pledged to build the most diverse government in modern history, and he and his team often speak about their desire for his administration to reflect America. He is being watched to see whether he will make history by nominating the first woman to lead the Pentagon, the Treasury Department or the Department of Veterans Affairs or the first African American at the top of the Defense Department, the Interior Department or the Treasury Department.