US President Donald Trump will reportedly nominate Amy Coney Barrett, a favourite of social conservatives, to be the new Supreme Court justice.
The president's decision - to be revealed at the White House on Saturday - has been confirmed to the BBC's US partner CBS News and other US media.
She would replace liberal Justice Ruth Bader Ginsburg, who died last Friday.
The nomination will touch off a bitter Senate fight to get her confirmed as November's presidential election looms.
CBS - citing several sources involved in or familiar with the selection process - reported that the president had settled on Judge Barrett.
But when asked about his choice on Friday evening, Mr Trump refused to give anything away: "You'll find out tomorrow. Look, they're all great. It could be any of one them."
If Judge Barrett is confirmed, conservative-leaning justices will hold a 6-3 majority on America's highest court for the foreseeable future.
The 48-year-old would be the third justice appointed by this Republican president, after Neil Gorsuch in 2017 and Brett Kavanaugh in 2018.
Coney Barrett is described as a devout Catholic who, according to a 2013 magazine article, said that "life begins at conception". This makes her a favourite among religious conservatives keen to overturn the landmark 1973 Supreme Court decision that legalised abortion nationwide.
Her links to a particularly conservative Christian faith group, People of Praise, have been much discussed in the US press. LGBT groups have pointed out that the group's network of schools have guidelines stating a belief that sexual relations should only happen between heterosexual married couples.
One such group, Human Rights Campaign, has voiced strong opposition to Judge Barrett's confirmation, declaring her an "absolute threat to LGBTQ rights".
She has repeatedly insisted her faith does not compromise her work.
Judge Barrett has also ruled in favour of President Trump's hardline immigration policies and expressed views in favour of expansive gun rights.
Conservatives hope she will help to invalidate Obamacare, the health insurance programme that was introduced by President Trump's democratic predecessor, Barack Obama.
Some 20 million Americans could lose their health coverage if the court overturns the Affordable Care Act (ACA).
Democrats have rallied support over this issue, but it is thought unlikely that the Supreme Court will rule on the ACA before the 3 November election.
Nominated by Mr Trump to the Chicago-based 7th Circuit Court of Appeals, Judge Barrett was confirmed by the Senate in a 55-43 vote in October 2017 after a tough process. She was one of the names the president considered to replace Justice Anthony Kennedy in 2017.
After graduating from Notre Dame University Law School in Indiana, she clerked for the late Justice Antonin Scalia, who died in 2016. She served as a legal scholar at Notre Dame for around 15 years.
Born in New Orleans, she is married to a former federal prosecutor in South Bend, Indiana, and together they have seven children.
Two of them were adopted from Haiti and their youngest biological child has Down Syndrome.