Elena Kagan has been sworn in as the fourth woman to serve on the US Supreme Court and the court's first chief justice in some 40 years with no experience as a judge, Press TV reported.
Taking both the constitutional oath and the judicial oath in the Supreme Court building in Washington on Saturday, Kagan swore to "administer justice without respect to persons, and do equal right to the poor and to the rich," The New York Times reported.
The ceremony came two days after the former dean of the Harvard Law School was confirmed by the Senate on a generally partisan vote of 63 to 37.
Replacing Justice John Paul Stevens, the court's retiring liberal leader, Kagan is the third woman to serve on the current court, and the first since William H. Rehnquist 38 years ago to join the court without experience as a judge.
President Barack Obama did not attend Saturday's ceremony, but at a televised celebration on Friday in the East Room of the White House, he expressed hope that the addition of a third woman would make the court "a little more inclusive, a little more representative."
After Obama's remarks, Kagan vowed to uphold the rule of law, saying she would "work my hardest and try my best to fulfill these commitments and serve this country I love as well as I am able."
During the Senate vote on Thursday, most Republicans opposed her selection, citing her lack of judicial experience and liberal views on issues like abortion, guns, and gay rights. They also criticized her for barring military recruiters from using a Harvard facility because of the rule banning homosexuals from serving openly.
She "would ally herself not with the constitutional liberties of all Americans, but with the big government agenda of the president who nominated her," said Senator Jeff Sessions of Alabama.