WASHINGTON (CNN) -- President Bush -- who had wanted an up-or-down vote on his Supreme Court nominee, Samuel Alito, by the end of the year -- said Friday he was disappointed that hearings on his nominee will not begin until January."Sam Alito Jr. is a incredibly intelligent, well-qualified person who should be on the court," Bush said while attending the Summit of the Americas in Mar del Plata, Argentina. "I told the leadership I thought it would be best to have the hearings before Christmas. They didn't feel like they could get the job done.""Fortunately there is a firm date and we look forward to working on that date," Bush said.Thursday leaders of the Senate Judiciary Committee said the confirmation hearings for Alito, who would replace the retiring Justice Sandra Day O'Connor, would begin January 9.Committee Chairman Arlen Specter said that "simply couldn't be done" because of the volume of writings Alito has produced in 15 years as a judge.The Pennsylvania Republican said senators need time to comb through about 300 opinions the New Jersey-based nominee has issued on the 3rd U.S. Circuit Court of Appeals."We have to do it right. We can't do it fast," Specter said.He said the committee's staff was stretched "very, very thin" by the confirmation process for Chief Justice John Roberts, who was confirmed in September, and by the failed nomination of White House Counsel Harriet Miers, who dropped out of the process last week.Specter said a vote by the full Senate tentatively scheduled for January 20. (Watch: Why one liberal backs Alito -- 2:26)O'Connor announced her retirement in July after nearly a quarter-century on the Supreme Court. She agreed to remain until her successor could be confirmed.That process was delayed when Roberts, her designated replacement, was instead tapped to replace Chief Justice William Rehnquist after Rehnquist's death in September. Then Miers withdrew last week amid sharp criticism from Bush's conservative allies, who questioned her credentials.By contrast, Alito, 55, is considered a darling of the movement, though top Justice Department officials advocating his confirmation Thursday sought to portray him as a "mainstream" federal judge."You can't pigeonhole him. He's not pro-plaintiff. He's not pro-defendant," said a senior Justice Department lawyer, who spoke to reporters on condition of anonymity. "It's unfair to pull out one or two cases and say he has inclination one way or another."Specter and Vermont Sen. Patrick Leahy, the committee's ranking Democrat, urged interest groups on both sides of the political spectrum to hold their fire on Alito."Virtually anybody who either voted for John Roberts or against John Roberts said the hearings were fair, and they learned enough to make up their mind," Leahy said.Alito "made a very good initial impression" in meetings with senators this week, but "we're only Monday, Tuesday, Wednesday, Thursday into the process," Specter said.McCain predicts confirmationEarlier Thursday, the influential group of Senate moderates known as the "Gang of 14" emerged from their first meeting on the nomination with the message that "everyone is reserving judgment on everything," in the words of Sen. Mark Pryor, an Arkansas Democrat.The group -- which earlier this year reached a compromise to head off a showdown over several Bush nominations for the federal courts -- could have tremendous sway over Alito's fate, particularly if Senate Democrats attempt to filibuster the conservative judge."It's way too early to talk about some of the more divisive things that have been talked about in the past," Sen. Ben Nelson, a Nebraska Democrat, said after the meeting, which lasted about 30 minutes."We're going to let the process unfold, make up our minds as we go along. But nobody's talking about those issues that would break up the gang or cause a rule change or a filibuster," Nelson said."Some of us are more favorably disposed than others," said Sen. John McCain, an Arizona Republican who held the meeting.McCain said he is "very favorably disposed" toward Alito, but "it's my obligation to go along with the Gang of 14 and have periodic meetings and discussions."The former presidential candidate later told CNN that he expected Alito to be confirmed.Republican Sens. Mike DeWine of Ohio, Lindsey Graham of South Carolina, and Olympia Snowe of Maine have said they don't see Alito triggering the "extraordinary circumstances" standard the group had set that could initiate a filibuster."Judge Alito's nomination has been here a week," McCain said. "To make a conclusion before even one hearing is held is not the way the 14 are going to function, as far as I know."Alito continued making the rounds on Capitol Hill on Thursday, meeting with more of the senators who will help decide whether he is to sit on the nation's highest court. He met with at least four members of the Gang of 14, including McCain, Pryor, West Virginia Democrat Robert Byrd and Rhode Island Republican Lincoln Chafee.CNN's Ted Barrett and Terry Frieden contributed to this report