President George W Bush has nominated federal appeals court judge Samuel Alito to the US Supreme Court.
President Bush praised Samuel Alito's broad judicial experience
He described Mr Alito as "one of the most accomplished and respected judges in America" and urged the Senate to quickly approve his nomination.
Mr Alito, seen as a conservative, said the role of a Supreme Court justice was to interpret, not make, the law.
The leader of the Democrats in the Senate has warned Mr Alito may face opposition in confirmation hearings.
Mr Bush's first choice, Harriet Miers, withdrew after Democrats questioned her judicial credentials and conservative Republicans her views on key issues.
The new nomination comes at a tense time for the White House, with a senior aide to Vice-President Dick Cheney charged last week in connection with a CIA leak.
If approved by the Senate, the 55-year-old Mr Alito will take the place of Justice Sandra Day O'Connor, who often held the swing vote in the court.
Announcing the nomination, Mr Bush stressed Mr Alito's "extraordinary breadth of experience", saying he had a greater judicial record than any nominee in the past 70 years.
He urged the Senate to approve his choice in a quick up-or-down vote before the end of the year.
Mr Bush called Alito a "thoughtful judge who considers the legal merits carefully and applies the law in a principled fashion".
He went on: "I'm confident that the United States' Senate will be impressed by Judge Alito's distinguished record, his measured judicial temperament, and his tremendous personal integrity."
The BBC's Justin Webb in Washington says the choice of Mr Alito is likely to prove highly controversial.
As a supporter of restricting, if not entirely abolishing, the right of American women to have abortions, Mr Alito's selection would galvanise the conservative base of Mr Bush's Republican party but horrify the US left.
If he gets to the Supreme Court, he will be in a position to join forces with other social conservatives to reshape the culture of the nation, our correspondent adds.
Republican Senator John Cornyn has praised Mr Alito as a "man of outstanding character, who is deeply committed to public service", Reuters news agency reported.
But Senate Minority Leader Harry Reid, who leads the Senate Democrats, said he was disappointed by Mr Alito's nomination, warning he may prove "too radical for the American people".
Mr Reid and other Democrats had urged the president to pick a moderate, consensus candidate rather than bowing to pressure from conservative Republicans.
Mr Alito is considered a quiet and reserved member of the federal appeals courts, having sat on the Third Circuit in Philadelphia since 1990.
He is known for consistently conservative judgements, leading commentators to compare him to current Supreme Court Justice Antonin Scalia.
The justices of the Supreme Court have immense power and are appointed until they die, resign or are impeached.
In the near future, the court is expected to consider some of America's most bitterly contested social issues, including assisted suicide, abortion, same-sex marriage, human cloning and campaign finance law.