Nancy Pelosi, the trailblazing Democrat who as the first woman US House of Representatives speaker shepherded landmark legislation and led two impeachments, says she will give up her leadership role a day after Republicans secured control of the chamber.

Ms Pelosi announced in a spirited speech on the House floor on Friday morning (Australian time) that she would step aside after leading Democrats for nearly 20 years.

Her decision also follows the brutal attack on her husband, Paul, last month in their San Francisco home.

“Now we must move boldly into the future,” said Ms Pelosi, who has served as Speaker from 2007 to 2011 and again from 2019.

“The hour has come for a new generation.”

A 82-year-old California liberal, Ms Pelosi’s announcement drew applause from Democrats even as many Republicans decided not to attend. She said she would continue to represent San Francisco as she has done for 35 years.

Ms Pelosi’s allies quickly rallied around Representative Hakeem Jeffries as her likely successor as the top House Democrat while Republicans prepared to install a Speaker who is expected to impede President Joe Biden’s legislative agenda.

In two stints as Speaker, Ms Pelosi played a central role in guiding the agenda of two Democratic presidents through Congress, even as she was vilified by many conservatives.

She helped pass president Barack Obama’s 2010 healthcare law as well as expansions of infrastructure and climate spending and gun regulations under Mr Biden. She also presided as the House impeached Republican president Donald Trump in 2019 and 2021.

Mr Biden called Ms Pelosi “the most consequential speaker of the House of Representatives in our history”.

Tweet from @BarackObama

House Democrats will vote on their leaders on November 30. Mr Jeffries, of New York, would be the first black lawmaker to lead one of the major parties in Congress. The No.2 House Democrat, Steny Hoyer, endorsed Mr Jeffries for the party’s leadership post and will seek a leadership job.

Following last week’s midterm elections, Republicans on Wednesday finally nailed down a slim majority in the House for the next Congress to be sworn in on January 3.

They offered initial support for Kevin McCarthy, who has had chilly relations with Ms Pelosi, to serve as Speaker. Mr McCarthy did not attend Pelosi’s speech.

With Democrats retaining control of the Senate, the divided Congress could make passage of even critical legislation tricky. Republicans said they planned to use their House majority to launch investigations into Mr Biden’s administration and family.

Ms Pelosi delivered a sentimental speech calling the House chamber “sacred ground” and remembering visiting the Capitol as a child when her father was sworn in as a congressman.

She recounted working with three presidents – Republican George W Bush as well as Mr Obama and Mr Biden. She did not mention Mr Trump but she alluded to the January 6, 2021, attack on the US Capitol by his supporters.

“American democracy is majestic, but it is fragile. Many of us here have witnessed our fragility firsthand, tragically in this chamber. And so democracy must be forever defended from forces that wish it harm,” Ms Pelosi said.

She also noted the increase in women and minority lawmakers since she joined the House in 1987.

She was the highest-ranking and most powerful elected woman in US history until Kamala Harris became vice-president in 2021. She also helped the party to stem its losses during the midterms, when Democrats lost fewer House seats than expected

Mr Pelosi had been under pressure from younger House Democrats to yield power. Mr Jeffries, 52, would herald a new generation of House leadership for the Democrats.

Before her announcement, Ms Pelosi had said the October 28 assault on her husband by a politically motivated hammer-wielding intruder in their San Francisco home factored in her decision.

– AAP