U.S. Senate Democrats have blocked two more of President Bush's judicial nominees following a Republican-led marathon debate, raising to six the number of obstructed nominations to date.

The Republican majority in the 100-member Senate has the 51 votes required to confirm the judicial nominees.

But they do not have the 60 votes necessary to end Democrats' delaying tactics, or filibusters, that have blocked the nominations from coming to a vote.

A filibuster is a method by which a minority of Senators tries to obstruct a measure favored by the majority by continuously talking.

Democrats on Friday blocked two more of President Bush's judicial nominees: Carolyn Kuhl and Janice Rogers Brown, both nominated to the federal appeals court.

The move came despite a nearly 40-hour, non-stop debate on the Senate floor, in which Republicans criticized Democrats' tactics as unprecedented and unconstitutional.

Senator Rick Santorum, the third-ranking Republican in the Senate, spoke after the Senate votes that failed to end the Democrats' filibusters.

"This is a very dangerous thing that happened here today," he said. "It will not serve this country well. It will politicize a branch of the government that here-to-for had stayed fairly apolitical. It is a mistake."

Senate Democrats defend their tactics as within the rules of the Senate. They note they helped confirm 168 of Mr. Bush's judicial nominees, only blocking a small percentage, whom they consider too conservative.

Senator Dianne Feinstein is a member of the Senate Judiciary Committee.

"I think the overwhelming number of the small percentage of individuals who were filibustered clearly indicates that we have the right and the obligation to do this, if their credentials are not such that we can assure Americans that they will act in the mainstream of legal thinking in this country," she said.

The non-stop Senate debate, which began Wednesday evening and ended Friday morning, was the longest in some 15 years.

Even though half a dozen of Mr. Bush's judicial nominees are stalled, Republicans are claiming victory, saying their marathon debate focused Americans' attention on what they call the Democrats' unconstitutional filibusters.

Democrats say victory belongs to them because the debate showed the Republicans are focused on the wrong issues and wasted two days that could have been used on legislation to improve the U.S. economy and health care.