Brett Kavanaugh's Supreme Court seat looks all but confirmed after he won the backing of key senators despite an FBI investigation into sexual assault allegations.

Republican Senator Susan Collins and Joe Manchin, a Democrat, both indicated their backing for the judge on Friday.

Judge Kavanaugh's confirmation would tilt America's highest court in favour of conservatives.

The court has the final say on issues such as abortion and gun control.

A final vote on whether Judge Kavanaugh will join the nine-member panel is scheduled for Saturday. If confirmed, the position is for life.

Hours before the undecided senators indicated their backing, the US Senate narrowly advanced President Donald Trump's nominee to a final vote by voting to strictly limit debate on the issue.

Senator Collins ended hopes she would side with Democrats in the final vote, telling fellow senators she did not believe the "charges can fairly prevent Judge Kavanaugh from serving on the court".

"The facts presented do not mean that Professor Ford was not sexually assaulted that night or at some other time but they do lead me to conclude that the allegations failed to meet the more likely than not standard," she said. (BBC)