By Jeff Zeleny, Kate Sullivan and Tami Luhby, CNN

(CNN) -- President-elect Joe Biden is nominating California Attorney General Xavier Becerra to lead the Department of Health and Human Services, the transition team announced Monday along with other key members of the incoming administration's health team.

If confirmed by the United States Senate, Becerra would serve a critical role in the administration's response to a pandemic that has killed more than 282,000 Americans as of Monday morning.

The transition team also announced other key members of Biden's health team including Dr. Vivek Murthy for surgeon general; Dr. Rochelle Walensky as director of the Centers for Disease Control and Prevention; Dr. Marcella Nunez-Smith as chair of the Covid-19 Equity Task Force; Dr. Anthony Fauci as chief medical adviser to the President on Covid-19 and director of the National Institute of Allergy and Infectious Diseases; Jeff Zients as coordinator of the Covid-19 response and counselor to the President and Natalie Quillian as deputy coordinator of the Covid-19 response.

Becerra, a former member of Congress, emerged as the leading contender for the critical role leading HHS after other candidates with more health care expertise were ruled out.

The New York Times was first to report Becerra's expected nomination.

Becerra is the first Latino to serve as the attorney general of California and has been in the post since 2017. He has been a fierce opponent of President Donald Trump, and the state of California has brought more than 100 lawsuits against the President and his administration's policies.

More than half of the lawsuits are over environmental policies, according to the Los Angeles Times, that the Trump administration had either put in place or removed. Becerra has also been a leader in the fight to protect the Deferred Action for Childhood Arrivals program, an Obama-era program that Trump has attempted to abolish that has shielded from deportation certain undocumented immigrants who came to the US as children.

One of Becerra's highest-profile health care roles recently has been chief defender of the Affordable Care Act in court.

With the Trump administration joining a coalition of Republican state attorneys general fighting to invalidate the landmark health reform law, Becerra has led a group of Democratic attorneys general arguing why the law remains valid. At issue is whether Congress' reducing the penalty for not having health insurance to zero rendered the individual mandate unconstitutional, which would cause the entire law to fall.

"COVID-19 has made one thing undeniable: We must safeguard the Affordable Care Act -- lives depend on it," Becerra said last month, just before the Supreme Court heard oral arguments on the case, which originated in Texas. "As if on cue, the Trump Administration cavalierly continues its march to dismantle the ACA and strip Americans of their health care. We will do everything we can to defeat this unprecedented assault on a critical federal law by a sitting president."

In particular, Becerra has pointed to the Affordable Care Act providing coverage for 20 million Americans through Medicaid expansion or the Obamacare exchanges, guaranteeing protections for millions of people with pre-existing conditions and funding state and local public health systems.

"Becerra has tackled some of the big health care issues he would face as HHS secretary, including reinvigorating the ACA and taming health care costs," said Larry Levitt, executive vice president for the Kaiser Family Foundation. He "has a demonstrated ability to speak to the public about the complexity of health care issues, which is an important part of the job."

In 2018, Becerra filed a lawsuit against Sutter Health, a system of 24 hospitals and more than 12,000 doctors in Northern California, for using anti-competitive practices to consolidate market power, resulting in higher health care prices. The attorney general secured a $575 million settlement a year ago that requires Sutter to change some of its practices.

Last week, Becerra submitted comments on behalf of a coalition of attorneys general opposing a new Trump administration proposal to automatically sunset HHS regulations that the agency doesn't review within two years.

"This rule is an attempt by the outgoing Trump Administration to make it more difficult for President-elect Biden and his incoming administration to put in place useful policies that will see our country through the pandemic," he said.

Affordable Care Act advocates praised Biden's pick Sunday night.

"Attorney General Xavier Becerra has all the skills and qualifications necessary to execute President-elect Biden's bold plans to increase access to quality care, lower skyrocketing prescription drug prices, make health care more affordable, strengthen Medicare and Medicaid and work to get the coronavirus pandemic under control," said Brad Woodhouse, executive director of Protect Our Care, which has sought to counter GOP attacks on the law.

Becerra served 12 terms in Congress as a member of the US House of Representatives and held several leadership posts. He was the chair of the House Democratic Caucus, the chair of the Congressional Hispanic Caucus and the ranking member of the Ways and Means Subcommittee on Social Security. He was also the first Latino to serve as a member of the Ways and Means Committee.

He sat on the Ways & Means subcommittee on health, where he worked on major health programs, such as Medicare.

He also served one term in the California Legislature and is a former deputy attorney general with the California Department of Justice.

Becerra was also under consideration to serve as US attorney general, CNN previously reported.

New Mexico Gov. Michelle Lujan Grisham, Rhode Island Gov. Gina Raimondo and former Michigan Gov. Jennifer Granholm had also been mentioned as potential contenders for the post, CNN previously reported.

Biden had been facing pressure from members of the Congressional Hispanic Caucus to nominate Lujan Grisham, who is the first Democratic Latina to be elected governor in the United States, to lead HHS. Members of the caucus have also been pushing for either Becerra or Democratic National Committee Chair Tom Perez to serve as US attorney general. The push has been part of a broader effort to pressure Biden to name multiple Latino or Latina nominees to top posts in his administration.

CHC Chairman and Texas Rep. Joaquin Castro said in a statement Sunday night that his caucus welcomed the news of Becerra's nomination.

"In this moment of crisis with COVID-19 devastating Latino communities, the Congressional Hispanic Caucus is proud that California's Attorney General Xavier Becerra, a dedicated public servant, will be nominated by President-Elect Biden to lead the U.S. Department of Health and Human Services," Castro said in a statement.

"We welcome the news of Becerra's nomination, and the CHC is encouraging President-Elect Biden to appoint five Latinos in the Cabinet, including Latinas in prominent positions," according to the statement. "We will continue to work in partnership with the Biden-Harris transition team to assemble the most diverse administration in American history."

Members of the caucus met with leaders of Biden's transition team last week and expressed frustration with how they believe Lujan Grisham had been treated in the Cabinet selection process. They took issue with what they said were leaks from the transition team about the governor turning down a Cabinet position to lead the Department of Interior, and said the leaks had the effect of being embarrassing for the governor.

Murthy, a doctor of internal medicine, served as US surgeon general under the Obama administration from 2014 to 2017.

The President-elect also announced Fauci as his medical adviser on Covid-19. Fauci will continue in his role as director of the National Institute of Allergy and Infectious Diseases

Biden told CNN's Jake Tapper in an interview last week that he had asked Fauci to stay on in his role as director and to serve as a chief medical adviser to his administration.

Biden has settled on Jeffrey Zients to serve as his White House coronavirus coordinator. Zients was a top economic adviser under President Barack Obama and is credited with reviving the Obamacare enrollment website, Healthcare.gov, after it was plagued with issues and crashed shortly after its launch in 2013.

This story has been updated with additional information.