WASHINGTON - The U.S. Senate ground to a halt yesterday as one West Virginia Democrat, his hands trembling and his voice raised, refused to yield the floor.

Sen. Robert C. Byrd, the 84-year-old master of Senate rules and procedures and fierce protector of congressional prerogatives, was issuing a plea as the senators debated a measure authorizing President Bush to attack Iraq.

"Give the Senate more time," the silver-haired Byrd implored. "We are being hurried into making a decision that is premature."

In a chamber ruled by consensus and subject to a web of arcane procedures, Byrd, an authority on the Senate where he has spent 44 years, is single-handedly delaying a vote on a war resolution. The resolution, expected to be approved by a wide bipartisan majority, would give Bush the power to launch a unilateral invasion of Iraq.

"This is a fateful decision - it involves a precedent in this country," Byrd declared yesterday. "It involves the blood of our fighting men and women. It is too momentous, too far-reaching of a decision to be signed, and sealed and delivered at 10:15 a.m. [Thursday] morning."

That is the appointed hour today when the senators are to vote to limit debate on the resolution, setting the stage for its final approval by the end of the week. The House is expected to approve the resolution today.

Byrd knows his actions won't block the likely Senate approval of the measure. Yet he is determined to prolong the debate to give the chamber more time to weigh the vast consequences of its decision - for the course of American history and for the precedent it sets in Congress.

It's a role Byrd has often embraced in the Senate, where he is second in seniority only to Republican Strom Thurmond of South Carolina, who turns 100 in December and is retiring after 48 years.

This summer, Byrd forced the Senate to put off action on Bush's proposed Homeland Security Department. Byrd argued against handing the president authority over such a sprawling new super-agency.

As the Bush administration has made national security its top priority during a politically charged election season, Byrd has styled himself as the chief obstacle - willing to spend hours on the Senate floor criticizing a popular president on the most sensitive of issues.

"I don't think about that," Byrd said in an interview yesterday about his role in holding up Bush's national security agenda. "I'm thinking about what we're about to do" in Iraq.

"This thing has been rammed and forced too fast."

With less than four weeks till the midterm elections, dissent has quieted in Congress to Bush's requested war resolution, which would allow him to use force against Iraq - acting alone if necessary - to disarm Saddam Hussein. But Byrd has continued to inveigh against the measure, and particularly Bush's insistence that Congress approve it before the elections.

Waving his well-worn miniature copy of the Constitution - always tucked in his breast pocket and often brandished during impassioned speeches - Byrd has warned darkly against expanding presidential power at the expense of Congress'.

"This is a blank check," he said. "Congress is ceding, lock, stock and barrel, its power to declare war - handing it over to a chief executive. Congress might as well just shut the door and put a sign up there that says, 'Going fishing.'"

Byrd's command of the rules, combined with his seniority and influence - he leads the Appropriations Committee, the heart of Congress' power of the purse - makes him a formidable obstacle in a chamber where any one senator's objection can block a proposal.

"Nobody," Byrd declared yesterday, "has ever used the rules of the Senate more than I have."

He also has a well-deserved reputation, in Washington and back home, for steering federal money to his state in the form of popular projects.

Known for his flowery speeches - which often meander from the issue at hand to ancient Rome, to rhapsodic tributes to his wife, Erma, and even his new dog, Trouble - Byrd can frustrate his colleagues. Often at the last moment, after key lawmakers have cut deals to smooth a measure's consideration on the Senate floor, aides will grouse that there's a "Byrd problem." That is usually synonymous with long delays and parliamentary knots.