US President-elect Joe Biden is expected to nominate former Federal Reserve Chair Janet Yellen as US Treasury Secretary.

The appointment will break a 231-year gender barrier and puts a seasoned economist and labour market expert in charge of leading the country out of the steepest downturn since the Great Depression. 

The move will shift Treasury's focus heavily toward progressive efforts to tackle growing economic inequality and fighting climate change and away from the Trump administration's pre-pandemic emphasis on cutting taxes and easing financial regulations. 

Yellen, 74, brings Biden decades of economic policy experience and is respected by Congress, international finance officials, progressives and business interests alike. 

She has called for opening fiscal spending taps to revive an economy wracked by the coronavirus pandemic and would be the first person to head the Treasury, the Fed and the White House Council of Economic Advisers. 

The post will present a host of new challenges for Yellen, whose policymaking experience in the past 20 years has largely centred on monetary - rather than fiscal - policy.

It means a far more political role than that she played in her long career at the Fed, an institution that goes to great lengths to distance itself from partisan politics.

Janet Yellen made history in 2014 when she became the first woman to chair the Federal Reserve after serving for a decade as San Francisco Fed president and a Fed governor. 

Republican President Donald Trump declined to renew her term and replaced her with current Fed Chair Jerome Powell in 2018. 

Born in Brooklyn, New York, to a family doctor and a school teacher, Yellen earned a doctorate in economics from Yale in 1971 as the only woman in her class and taught at several major universities before serving as a top economic adviser to President Bill Clinton from 1997 to 1999. 

She is married to Nobel Prize-winning economist George Akerlof, whom she met in 1977 at the Fed where both were working in research roles.

At Treasury, Yellen would have a major role in influencing US fiscal and tax policy, tools she did not have at the Fed. 

Janet Yellen with former ECB chief Mario Draghi and former Bank of England chief Mark Carney

Yellen "will be a trusted, steady, and pragmatic hand on the helm as the U.S. navigates the economic recovery from the Covid-19 pandemic," said Tim Adams, a former Treasury official who is president of the Institute of International Finance, which represents more than 450 global banking firms. 

With Democrats having only a slim possibility of winning a US Senate majority in two Georgia runoffs in January, Yellen faces tough negotiations with Republicans to try to push Biden's agenda, includes raising taxes on the wealthy and investing trillions of dollars in infrastructure, education and fighting climate change. 

Economists said Yellen would be effective in articulating the economic arguments for spending more in the near term to boost job growth and reduce the gap between rich and poor. 

Yellen's 2014 speech highlighting the fast growth of US inequality suggested it was a threat to "values rooted in our nation's history." 

Investors see Yellen as a force for more fiscal action to combat the economic crisis unleashed by the Covid-19 pandemic, and as someone in a strong position to ensure the Treasury will continue to work closely with the Fed. 

She was chosen over other seasoned economic policymakers, including current Fed Board of Governors member Lael Brainard, 58, who served as the Treasury's undersecretary for international affairs early in the Obama administration. 

Also under consideration was Roger Ferguson, 69, president of retirement asset manager TIAA and a former Fed vice chair, who would have been the first Black Treasury secretary. 

Senator Elizabeth Warren, a rival to Biden for the Democratic presidential nomination and a candidate for the Treasury post, tweeted that Yellen would be "an outstanding choice" and praised her for having "stood up to Wall Street banks" as Fed chair.