President Bush gave Supreme Court nominee Samuel Alito a broadcast boost Saturday, calling for a simple up-or-down Senate confirmation vote despite a blocking effort by some Democrats.

A final vote on whether to make the conservative federal appellate judge the nation's 110th Supreme Court justice is scheduled for Tuesday unless opponents win an uphill battle to impose a filibuster.

"The Senate has a constitutional responsibility to hold an up-or-down vote on Judge Alito's nomination," Bush said in his weekly radio address. "Throughout its 216-year history, the Senate has held an up-or-down vote on every Supreme Court nominee with majority Senate support."

The president spoke as liberals led by Sens. Edward Kennedy and John Kerry, D-Mass., worked to deprive supporters of the 60 votes needed to limit debate. They faced resistance from some fellow Democrats as well as solid Republican opposition to the stalling tactic.

Alito, a former federal prosecutor and Reagan administration lawyer, would replace retiring Justice Sandra Day O'Connor. She is the court's first female justice and the swing vote on several 5-4 rulings that maintained abortion rights, preserved affirmative action and limited the application of the death penalty.

"Sam Alito is a man of great character and integrity," Bush said in his broadcast, citing accolades Alito has received from fellow judges on the Philadelphia-based 3rd U.S. Circuit Court of Appeals, including seven who testified on his behalf.

"He has more prior judicial experience than any Supreme Court nominee in more than 70 years," the president said. "He understands that the role of a judge is to strictly interpret the law, not to advance a personal or political agenda."

Senate leaders say Alito has enough bipartisan support to overcome any filibuster attempt by minority Democrats, many of whom contend that Alito's confirmation would jeopardize individual rights and liberties.

Kennedy, in a letter to his colleagues, says Alito has ruled against women, minorities, and the disabled in job discrimination claims, and supports powerful presidential authority.

"We want our country to be safe and we expect our president to do all he can to protect us," Kennedy said. "But we want the White House to obey the law. We want a court that will blow the whistle when the president is out of bounds."

Kerry, defeated by Bush for the presidency in 2004, called for a filibuster Thursday while attending a world economic conference at a Swiss resort.

Asked Friday if the administration was taking Kerry's call seriously, White House press secretary Scott McClellan chuckled and said:

"It was a pretty historic day. This was the first time ever that a senator has called for a filibuster from the slopes of Davos, Switzerland. I think even for a senator, it takes some pretty serious yodeling to call for a filibuster from a five-star ski resort in the Swiss Alps."