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 White House election looms.

CBS - citing multiple sources involved in or familiar with the selection process - reported that the president had settled on Judge Barrett.