WASHINGTON — The death late Saturday of Chief Justice William H. Rehnquist opened a second front in the ideological battle over the Supreme Court, with President Bush saying Sunday that he would act quickly to replace him and Senate Republicans planning a one-week delay in the hearings to fill the seat being vacated by Justice Sandra Day O'Connor.

By creating a second vacancy, Rehnquist's death gave Bush a chance to put a deeper stamp on the court and immediately raised the stakes in the partisan clash over the composition of the judiciary. But it came at an extraordinarily difficult time for the White House, which is under intense criticism for its response to the devastation from Hurricane Katrina.

The chief justice's death seemed unlikely to lead to any fundamental alteration in the balance of the court. Rehnquist — unlike O'Connor, who has been a swing voter on the most contentious issues — was a stalwart conservative, and Bush is all but certain to choose someone from the same mold to replace him, though he is under some pressure to choose a Hispanic or a woman rather than a white man.

The chief justice died just days before the Senate Judiciary Committee was to convene hearings on the nomination of one of his former clerks, Judge John Roberts of the District of Columbia U.S. Circuit Court of Appeals, to replace O'Connor. The hearings — the first in 11 years for a Supreme Court nominee — were to begin Tuesday.

But as Senate leaders sought to accommodate the funeral plans and Democrats pressed for a delay partly on the grounds that the government needed to focus on the crisis along the Gulf Coast, a senior Senate Republican aide said the Roberts hearings are expected to be postponed for a week. Dan Bartlett, Bush's counselor, said he expected the Senate leadership to announce an unspecified delay in the proceedings.

Rehnquist died Saturday evening at his home in Arlington, Va. He was 80, and had served on the court for 33 years, the last 19 as chief justice. The court announced Sunday evening that his body would lie in repose in the Great Hall of the Supreme Court on Tuesday and Wednesday, and that he would be buried in Arlington National Cemetery after a private service Wednesday afternoon at St. Matthew's Cathedral in Washington.

"He was a man of character and dedication," Bush said during an appearance Sunday morning in the Roosevelt Room of the White House, recalling how the chief justice, rendered frail by illness and treatment, had mustered the strength to swear him in for his second term on Jan. 20. "His departure represents a great loss for the court and for our country."