Conservative federal Judge John Roberts has won US Senate confirmation and has been sworn in as the 17th chief justice of the United States.
Judge Roberts is President George W Bush's first nominee to the Supreme Court.
He is replacing William Rehnquist, who died on 3 September after being the court's conservative anchor for 33 years.
The 50-year-old is the youngest chief justice in two centuries and is expected to hold the lifetime post for decades.
A federal appeals court judge for the past two years, he was earlier one of the country's top lawyers and served in both the Reagan administration and the first Bush administration.
Judge Roberts' legal credentials have gone unchallenged, but foes have questioned his commitment to civil rights and women's rights.
They have also complained about his refusal at his Senate confirmation hearing this month to disclose how he might rule on issues such as abortion rights.
He testified that it would be improper to prejudge cases that might come before him and that he would serve on the highest court without a political agenda.
