WASHINGTON — Vice President Dick Cheney said yesterday he is prepared to cast the tie-breaking vote, if necessary, to change Senate rules and bar Democrats from using filibusters to block President Bush's judicial nominees.

"I would support an effort to restore the constitutional practices that existed before the Democrats started using the filibuster for judicial appointments," Cheney said aboard Air Force Two as the Senate stands on the brink of a partisan showdown on the issue.

If Senate Majority Leader Bill Frist launches an effort to bar filibusters of judicial nominations — a step that senior aides say is imminent and is known as the "nuclear option" because Democrats say they would retaliate by blocking all but the most crucial legislation for the rest of the two-year congressional session — Cheney said he, as Senate president, would back the move.

"If the decision is made" to change the rules, Cheney said, "I would certainly work with Senator Frist to achieve our objective."

The vice president brushed aside the concerns of some, including a handful of Republicans, that changing the rules would trample on minority rights and could backfire for the party in a future Congress controlled by Democrats.

"Democrats are the ones who altered the traditional practice," he said. "It's important that that precedent not be allowed to stand."

Democrats have used filibusters, which invoke the right of senators to debate any matter indefinitely unless a two-thirds majority agrees to cut off discussion and vote, to block 10 of Bush's 200-plus nominees. With 55 seats, Republicans lack the 60-vote "supermajority" necessary to overcome them.

"If you allow that filibuster precedent to stand," Cheney said, "in effect you've raised the bar for confirmation of judicial appointments to say that you've now got to have 60 votes to get a judge confirmed. That was never the case before. That should not be the case now."

Still, Republicans have used those and other Senate tactics to hold up Democratic nominees for other posts in the past and have tried to use filibusters against Democrats' judicial picks. GOP leadership never provided a floor vote for 24 of former President Clinton's appellate-court nominees; only two received a committee hearing.

Democrats yesterday assailed Frist's decision to appear in a national telecast with prominent Christian conservatives — who are calling for elimination of the filibuster on federal judges.

The April 24 "Justice Sunday" telecast is sponsored by the Family Research Council, whose president, Tony Perkins, said in a letter: "We must stop this unprecedented filibuster of people of faith."

Several Democratic senators criticized Perkins' comments and Frist's planned participation, first reported in The New York Times.

"I am disappointed that in an attempt to hide what the debate is really about, Senator Frist would exploit religion like this," said Senate Minority Leader Harry Reid, D-Nev. "Participating in something designed to incite divisiveness and encourage contention is unacceptable. I would hope that Senator Frist will rise above something so beyond the pale."

Frist's participation in "Justice Sunday" was reported by The Washington Post.