WASHINGTON - Elena Kagan will be sworn in Saturday as a Supreme Court justice, becoming only the fourth woman in US history to win a seat of the nation`s highest court.

But the court`s conservative make-up is unlikely to change.

US Senators voted 63-37 Thursday to confirm Kagan as one of the nine justices who act as final arbiters of the US Constitution, set precedent for lower courts, and decide the nation`s toughest moral and legal dilemmas.

Five Republicans broke ranks to back the 50-year-old former Harvard Law School dean, and just one Democrat, Senator Ben Nelson of Nebraska, voted against her.

She will be sworn in by Chief Justice John Roberts, but will not be formally seated until October 1 for the court`s fall session.

Though never seriously in doubt, her confirmation to the lifetime post gave President Barack Obama and his Democratic allies a much-needed victory before November mid-term elections in which they are expected to suffer heavy losses.

Thanking the Senate, Obama said he was "confident that Elena Kagan will make an outstanding Supreme Court Justice."

The confirmation brought to two the number of justices named by the president -- after the court`s first Hispanic justice, Sonia Sotomayor -- and the total number of women on the high bench to three for the first time ever.

Kagan’s "legal qualifications are unassailable. She earned her place at the top of the legal profession," said Senator Patrick Leahy, chairman of the Senate Judiciary Committee.

"Her qualifications, intelligence, temperament and judgment will make her a worthy successor to Justice John Paul Stevens," he said, referring to the retiring leader of the court`s liberal bloc.

But Kagan was not expected to tip the overall ideological balance of the court, which many observers have described as the most conservative in decades.

Nominating US Supreme Court justices ranks among the most consequential powers of the US presidency, as a judge`s lifetime tenure typically stretches well beyond the influence of the temporary occupant of the White House.

Some of their most controversial decisions have included the 1973 Roe v. Wade ruling that legalized abortion in the United States and the Bush v. Gore case that handed the disputed 2000 presidential election to George W. Bush.

And some of the toughest rulings have come in 5-4 decisions that can take a generation to reverse.

The 50-year-old Kagan, who as US solicitor general has argued the Obama administration`s case before the high court, will be the youngest justice.

Democrats pointed to her decades of legal work, including in her current position as US solicitor general and her time as the first woman dean of Harvard Law School.

Her critics said they feared she would be unable to keep her personal politics separate from her judging and painted her as a foe of gun ownership and of restrictions on abortion.

"I`m not quite sure how I would characterize my politics, but one thing I do know is that my politics would be, must be, have to be, completely separate from my judging," Kagan told the Senate Judiciary Committee during her confirmation hearings.

She drew laughs from the packed committee room by saying some high court arguments "will put you to sleep," that judges sometimes have to act because lawmakers "make a mistake, they`re careless, whatever," and diplomatically declining invitations to criticize her potential future colleagues.

She also backed expansive "war on terrorism" government powers, saying she favored military tribunals for some suspected terrorists, in line with Obama`s policies.

Despite looming November elections to decide control of the US Congress, opposition to Kagan becoming the court`s 112th justice was relatively tepid.

Kagan drew the American Bar Association`s highest rating of "unanimously well qualified," and her nomination had the support of past solicitors general, including many Republicans.

She carefully avoided criticizing current members of the court despite being invited to do so during her confirmation hearings.

"I would not want to characterize the current court in any way," she said. "I hope one day to join it."

BDST: 12:44 HRS, August 07, 2010