WASHINGTON (AFP) -US President George W. Bush nominated a conservative appeals court judge, Samuel Alito, to the Supreme Court in a move that may heal a rift in the weakened leader”s Republican party.

In a joint appearance at the White House, Bush called Alito &#34one of the most accomplished and respected judges in America&#34 and urged the US Senate to hold a confirmation vote by the end of the year.

If approved, Alito would replace retiring Justice Sandra Day O”Connor, the first woman named to the highest court in the United States and frequently the deciding vote when the nine justices take up volatile issues like abortion.

The announcement came after one of the toughest weeks of Bush”s presidency, with new questions about the case for war in Iraq even as the death toll among US soldiers in the conflict passed 2,000.

On Thursday, Bush”s previous pick to replace O”Connor, longtime aide Harriet Miers, withdrew amid charges of cronyism and a revolt within the president”s Republican party from conservatives who doubted her ideological purity.

And on Friday, a senior Bush aide resigned after being charged with obstruction of justice and perjury in connection to a CIA leak investigation that still swirls around the White House.

Opposition Democrats greeted Alito”s nomination skeptically, but lack the Senate seats to defeat it in an up-or-down ballot. They could, however, try to derail confirmation with parliamentary tactics that indefinitely delay a vote.

&#34It is sad that the president felt he had to pick a nominee likely to divide Americans instead of choosing a nominee in the mold of Sandra Day O”Connor, who would unify us,&#34 said Democratic Senator Chuck Schumer.

&#34The Senate needs to find out if the man replacing Miers is too radical for the American people,&#34 said Harry Reid, Democratic leader in the Senate, who said he was &#34disappointed&#34 by the president”s choice.

Educated at Princeton and Yale universities, Alito, 55, was confirmed unanimously to the appeals court after being nominated by Bush”s father, former president George Bush, in 1990.

&#34As a Justice Department official, federal prosecutor and judge on the United States Court of Appeals, Sam Alito has shown a mastery of the law, a deep commitment of justice, and he is a man of enormous character,&#34 said the president.

&#34He has a deep understanding of the proper role of judges in our society. He understands that judges are to interpret the laws, not to impose their preferences or priorities on the people,&#34 said Bush.

The court wields enormous influence over American life as the final arbiter of the US Constitution and the ultimate court of appeal, and it has ruled on issues like abortion, the death penalty and civil rights. Justices are named for life but can step down.

&#34We are trusting that we are now on the fast-track to derailing Roe v Wade as the law of the land,&#34 said Troy Newman, president of Operation Rescue, an anti-abortion group.

Another conservative group, Catholic Priests for Life, acknowledged some senators would challenge Alito”s nomination on the grounds that it threatened &#34so-called ”abortion rights.”&#34

&#34But the American people are already deciding that their Constitution does not permit dismembering children,&#34 said Frank Pavone, the group”s national director.

The pro-choice National Organisation for Women (NOW) pledged to oppose the nomination over abortion.

&#34If Alito is confirmed by the US Senate, many of our fundamental rights will be at great risk,&#34 NOW president Kim Gandy warned.

&#34Federal judges have the duty to interpret the Constitution and the laws faithfully and fairly, to protect the constitutional rights of all Americans, and to do these things with care and with restraint, always keeping in mind the limited role that the courts play in our constitutional system,&#34 said Alito.

It was Bush”s third choice to replace O”Connor: He had initially settled on another appeals court judge, John Roberts, but changed his nomination to chief justice after William Rehnquist died.

Roberts, who enjoyed broad conservative support, easily won confirmation.

US conservatives hope Alito will swing the court solidly to the right on hot issues such as abortion and links between church and state.

But his record as a prosecutor and federal appeals court judge over a 28 year career is far more of a cautious constitutionalist than his conservative supporters and liberal detractors might believe, analysts say.

Law experts say Alito, a soft-spoken 55 year old Catholic and graduate of the elite Yale University law school, hates being labelled a conservative, or much of anything.

&#34He is very loathe to inject any social thinking into decisions,&#34 said constitutional scholar John McGinnis, of Northwestern University.

While McGinnis described him as a constitutional originalist — someone who sticks to the original text of the US Constitution for decisions — legal experts say Alito would not actively seek to overturn decisions made by earlier, less conservative Supreme Courts.

&#34He has a healthy respect for precedent,&#34 said Ronald Chen, the assistant dean of Rutgers University Law School, who has argued several cases before Alito.