Kavanaugh sworn in, Trump sorry for him

US Supreme Court Justice Brett Kavanaugh has sought to put a bruising confirmation battle behind him, being sworn in at a White House ceremony in which President Donald Trump declared him innocent of sexual misconduct and apologised for the heated process.

Kavanaugh, whose bid to join the top US court nearly failed after a California professor accused him of assaulting her when they were in high school, said he would enter his new job without bitterness despite a political fight that he said had destroyed his family and his name.

"The Senate confirmation process was contentious and emotional. That process is over. My focus now is to be the best justice I can be," he said at the White House, with his wife and children standing nearby.

Kavanaugh said he would aim to be a force for stability and unity on the court, whose other eight members all attended the ceremony.

"Although the Senate confirmation process tested me as it has tested others, it did not change me," he said.

Kavanaugh's confirmation proceedings exploded in controversy after Christine Blasey Ford went public with allegations that Kavanaugh sexually assaulted her in 1982.

Kavanaugh gave a forceful, emotional denial of those allegations during testimony before lawmakers that some Democrats said showed a lack of judicial temperament.

The Senate voted 50-48 on Saturday to confirm him, with just one Democrat supporting him.

His confirmation to the lifetime job was a victory for Trump and locked in a conservative majority on the court.

"On behalf of our nation, I want to apologise to Brett and the entire Kavanaugh family for the terrible pain and suffering you have been forced to endure," Trump said at the start of a ceremonial swearing-in.

"Those who step forward to serve our country deserve a fair and dignified evaluation, not a campaign of political and personal destruction based on lies and deception," he said.

Trump, under pressure from moderate Republican senators, ordered a brief FBI investigation, which he said found Kavanaugh innocent.

"A man or a woman must always be presumed innocent unless and until proven guilty," Trump said to applause. "And with that I must state that you, sir, under historic scrutiny, were proven innocent."