Democrats are gearing up to fight the nomination of Judge Samuel Alito for the US Supreme Court, a choice widely welcomed by conservative Republicans.
President Bush urged the Senate to approve Samuel Alito quickly
President George Bush put forward Mr Alito after his first candidate, lawyer Harriet Miers, withdrew when conservatives refused to support her.
Democrats fear Mr Alito could swing the court too far to the right and have threatened to block his nomination.
The ruling Republicans have praised his long record of conservative decisions.
If confirmed, Mr Alito would take the place of retiring Justice Sandra Day O'Connor, who has often held the swing vote in the court.
The Republicans hold a 55 to 45 seat majority in the 100-seat Senate, which must approve his nomination.
However, the opposition Democrats could prevent the confirmation vote by using the filibuster, a device which allows senators to block debate by talking non-stop.
They criticised Mr Bush for ignoring their calls for a consensus candidate.
"It is sad that the president felt he had to pick a nominee likely to divide Americans instead of choosing a nominee in the mould of Sandra Day O'Connor, who would unify us," said Democratic Senator Charles Schumer.
He said Mr Alito, an appeals court judge since 1990, "would make the court less diverse and far more conservative".
Fellow Democratic Senator Edward Kennedy also warned Mr Alito could "fundamentally alter the balance of the court and push it dangerously to the right".
"The filibuster's on the table," California Senator Barbara Boxer is quoted as saying by the Associated Press news agency.
Liberal interest group People for the American Way urged its 750,000 members to oppose a candidate "chosen to divide America", the AFP news agency reports.
However, Mr Alito's nomination has been welcomed by conservative Republicans and anti-abortion campaigners.
Senate Majority Leader Bill Frist warned he would not hesitate to move against filibusters if the Democrats forced him to.
And Arlen Specter, the Republican chairman of the Senate Judiciary Committee, said that unlike Ms Miers, Mr Alito had a long paper trail on which to assess his views.
James Dobson, founder of anti-abortion group Focus on the Family, said he was "extremely pleased" by Mr Alito's selection, AP reports.
Mr Bush, who described his nominee as "one of the most accomplished and respected judges in America", on Monday urged the Senate quickly to approve him.
The justices of the Supreme Court have immense power and are appointed until they die, resign or are impeached.