WASHINGTON (BBC) -- Conservative Judge Samuel Alito has been sworn in for a lifetime post on the U.S. Supreme Court after being approved by the Senate.

A majority in the chamber backed Judge Alito in a vote earlier on Tuesday despite a last-minute attempt by Democrat senators to block the move.

Judge Alito, 55, replaces Justice Sandra Day O'Connor, who often held the swing vote on key issues.

He is the second conservative Bush nominee to enter the U.S. Supreme Court.

The president's first, Chief Justice John Roberts, swore in Judge Alito at a private ceremony at the court.

A majority of the Republican-controlled Senate had pledged to support Judge Alito's confirmation in the final vote, which was decided by a simple majority. America is fortunate that this good and humble man is willing to serve

The deeply divided Supreme Court has the power to strike down laws passed by Congress and to rule on key issues.

The vote follows several days of debate in the Senate. "Judge Alito is extraordinarily well-qualified to serve on our nation's highest court, and America is fortunate that this good and humble man is willing to serve," President Bush said in a statement.

But Democratic Senator Edward Kennedy has warned that the judge's view on executive power would make the court too tame and remove its traditional check on the president. "Judge Alito would have enormous impact on our basic rights and our liberties for decades to come," he said.

The justices of the Supreme Court are appointed until they die, resign or are impeached.

Bush's earlier choice for the post, lawyer Harriet Miers, withdrew when conservatives refused to support her.