Senate Republicans leaders welcomed President Bush's nomination of federal appeals judge Samuel A. Alito Jr. to the Supreme Court today and called for quick confirmation, but Democrats described the pick as a sop to the extreme right and warned that they would not act hastily.

The choice of Alito, 55, a judge on the U.S. Court of Appeals for the 3rd Circuit based in Philadelphia, immediately ignited strong reactions from both sides of the abortion debate.

NARAL Pro-Choice America, an abortion rights group, declared its opposition and said Bush "gave into the demands of his far-right base" and chose a nominee who would threaten "fundamental freedoms, including a woman's right to choose."

The National Pro-Life Action Center, which opposes abortion, applauded the choice, pointing to Alito's lone dissent in a critical part of his appellate court's ruling in Planned Parenthood v. Casey. Alito dissented from the court's decision to strike down a provision requiring women to notify their husbands before obtaining an abortion. In 1992 the Supreme Court upheld the ruling, disagreed with Alito and used the case to reaffirm Roe v. Wade, the 1973 decision that legalized abortion.

Although some Democrats immediately voiced strong objections to Alito, it was not immediately clear whether they would attempt to block the nomination through a filibuster. Republicans have warned that such a move would reopen a major Senate battle over filibusters and possibly trigger the so-called "nuclear option" of banning them for judicial nominees.

Alito, accompanied by members of his family and Senate Majority Leader Bill Frist (R-Tenn.), visited the Capitol to pay tribute to the late Rosa Parks, an icon of the civil rights movement, as her body lay in honor in the Rotunda. Alito then began meeting with senior GOP senators as part of the process leading to confirmation hearings.

Frist said afterward the immediate reactions to Alito from Democrats and Republicans were to be expected. "There's going to be a lot of positioning from a political standpoint," Frist told reporters. "As leadership, we're going to plow through that, and we're going to stay above it. And it's going to be tough."

Sen. Arlen Specter (R-Pa.), chairman of the Senate Judiciary Committee and a supporter of abortion rights, said he would be "interested in Judge Alito's views on following precedents."

Alito, by his own account, "has worked hard to follow the precedents of the Supreme Court," Specter said. "And there is a lot more to the issue of a woman's right to choose than how you may feel about it personally. We have a long tradition in the court."

Specter said Alito has a "very distinguished record" that includes about 300 written judicial opinions and involvement in some 3,500 cases. Specter's committee will hold the Senate's hearings on Alito's nomination.

Sen. Ted Stevens (R-Alaska) said the Senate should "keep in mind the best interests of Justice Sandra Day O'Connor," who he noted has announced her retirement but is staying on "as a courtesy" until her successor is confirmed. Stevens said he hoped Alito would be confirmed in time to replace O'Connor when the Supreme Court meets in January.

Asked if he were apprehensive about the prospect of being the subject of a major Senate fight, Alito said, "Well, I'm just looking forward to working with the Senate in the confirmation process. And I will do everything I can to cooperate with them and to discuss my record as a judge and the record of what I've done during the other stages of my legal career."

Sen. Charles E. Schumer of New York, one of the most outspoken Democrats on the Senate Judiciary Committee, invoked the name of Rosa Parks, who died last week at age 92, in questioning Alito's commitment to civil rights.

"Like Rosa Parks, Judge Alito will be able to change history by virtue of where he sits," Schumer said. "The real question today is whether Judge Alito would use his seat on the bench, just as Rosa Parks used her seat on the bus, to change history for the better or whether he would use that seat to reverse much of what Rosa Parks and so many others fought so hard and for so long to put in place."

He called Alito's visit to pay respects to Parks "appropriate," but said his record "is much more important" and raises questions about his commitments to civil rights, workers' rights, women's rights and "the rights of average Americans." Schumer said it was "sad" that Bush chose "a nominee likely to divide America instead of choosing a nominee in the mold of Sandra Day O'Connor, who would unify us."

As for the timing of the hearings, Schumer said, "When there is a controversial nominee for a pivotal swing vote on the high court, the procedure should not be short-circuited, short-changed or rushed. We need to be careful here."

He refused to comment on the possibility that Democrats could try to block Alito through a filibuster. "Nothing is on the table, and nothing is off the table," he said. "Let's learn more about Judge Alito."

Frist indicated earlier that Republicans were prepared for a Senate fight over Alito, whom he called "a highly qualified nominee" with "impeccable" qualifications.

"If the Democrats look for a fight, we'll be there ready to fight," Frist said on the Fox News Channel. He said there would be "plenty of fodder for fights" in Alito's judicial record, "and we'll be ready to fight if we need to."

Frist added, "If it takes a fight on the floor of the United States Senate, people like Chuck Schumer and the Democrats are going to get that. The American people deserve fair up-or-down votes. . . . I hope it doesn't come to a filibuster. It should not; the American people deserve more."

The prospect of a filibuster raised the profile of the "Gang of 14," a group of seven Republicans and seven Democrats who broke with their parties in May to forge a compromise aimed at ensuring confirmation votes for three of Bush's appellate court nominees in return for shelving the "nuclear option." Under that option, the Republicans would have used a parliamentary maneuver to ban judicial filibusters by majority vote. The Democrats had vowed to retaliate by using Senate rules to bring most of the chamber's business to a halt.

The Gang of 14 played a crucial role because the Republicans hold 55 Senate seats, and 60 votes are required to end a filibuster. Under the compromise, the seven Democrats said they would not go along with Democratic filibusters of judicial nominees except in "extraordinary circumstances," a term that was left undefined.

There was no indication today whether any Democrats would invoke "extraordinary circumstances" to filibuster Alito.

Sen. Ben Nelson (D-Neb.), a leading Democratic member of the Gang of 14, said in a statement that "we should withhold judgment" until the hearings on Alito.

"I'm sure other members of the Gang of 14 agree that the process should unfold fairly and that Judge Alito should have his day before the Judiciary Committee," Nelson said.

Sen. John McCain (R-Ariz.), leader of the group's GOP members, said today the Gang of 14 would meet in the next couple of days, "and we'll try to see what everybody's temperature is." In an interview on MSNBC's "Imus in the Morning" program, McCain said, "I certainly would like to avoid filibustering and blowing up the Senate. . . . So we'll meet, and I'm sure that most people will want to, I hope, give Judge Alito a fair hearing and reserve judgment until he performs before the Judiciary Committee."

Sen. Harry M. Reid of Nevada, the Senate Democratic leader, said he was "disappointed" in the choice of Alito, whom he said will require "an especially long hard look by the Senate because of what happened last week to Harriet Miers," the White House counsel and long-time Bush loyalist whose nomination for the same Supreme Court seat was withdrawn in the face of conservative opposition.

"Conservative activists forced Miers to withdraw from consideration for this same Supreme Court seat because she was not radical enough for them," Reid said in a statement. "Now the Senate needs to find out if the man replacing Miers is too radical for the American people." He also complained that Bush "has chosen a man" to replace O'Connor, one of two women on the nine-member court, and did not opt for a Hispanic or someone who is not federal appellate judge.

"President Bush would leave the Supreme Court looking less like America and more like an old boys club," Reid said

Sen. Patrick Leahy of Vermont, the top Democrat on the Judiciary Committee, called the choice "a needlessly provocative nomination" and charged that Bush "has chosen to reward one faction of his party, at the risk of dividing the country."

He said the Miers nomination exposed a "right-wing litmus test" for Supreme Court nominees.

Sen. Edward M. Kennedy (D-Mass.), another member of the Judiciary Committee, said the nomination was "based on weakness, not on strength." In a statement, he said Bush "picked a nominee whom he hopes will stop the massive hemorrhaging of support on his right wing."

Although Alito "is clearly intelligent and experienced on the bench," Kennedy said, he could, if confirmed, "fundamentally alter the balance of the court and push it dangerously to the right."