The Supreme Court gave a cool reception to the Bush administration's plea to save the rules that federal judges use in sentencing offenders yesterday, with a slim but firm majority of the court casting doubt on the guidelines' constitutionality during a special two-hour oral argument.

At issue were the more than 400 pages of federal sentencing guidelines, created and annually revised by the seven-member U.S. Sentencing Commission to ensure uniform punishment across the country.

In June, the court voted 5 to 4 to strike down a similar set of sentencing guidelines used by Washington state because they permitted judges to increase a defendant's sentence based on facts that had not been proven to a jury or admitted in plea bargaining. That violated the Sixth Amendment right to a jury trial, the court ruled.

Acting U.S. Solicitor General Paul D. Clement seemed unable to convince any member of the five-justice majority from that case, Blakely v. Washington, that the federal guidelines should survive because they are created by a commission within the judiciary, rather than enacted legislatively, as the Washington rules had been.

"What is the difference in effect?" asked Justice David H. Souter. "That's where I am having trouble, and I guess some others are having trouble. . . . Whether it's a guideline or a statute, what difference does it make from the Sixth Amendment perspective?"

And, because the commission was established under a sentencing reform law passed by Congress in 1984, Justice Ruth Bader Ginsburg added, didn't that mean that "the critical finding has to be made by a jury?"

Except Justice Clarence Thomas, who maintained his customary silence, the other members of the Blakely majority, Justices John Paul Stevens and Antonin Scalia, also made comments or asked questions that strongly implied they were inclined to apply the logic of Blakely to the federal guidelines.

Yesterday's argument was set up on an expedited basis in response to a post-Blakely clamor from lower courts and federal prosecutors for a definitive Supreme Court ruling on the constitutionality of the 17-year-old guidelines.

After Blakely, federal criminal trials and plea negotiations across the country were cast into confusion. In one widely reported case, the North Carolina farmer known as "Tractor Man" was released because more than four years of his sentence for tying up downtown Washington while pretending to be armed were based on facts found by a judge, not a jury.

Yet, perhaps reflecting the fact that there was so little apparent flexibility on the basic issue before the court, the justices wrapped up the argument 12 minutes early after running out of questions for two lawyers representing the federal defendants who are challenging the guidelines.

The justices instead spent much of their time discussing what system, if any, they could devise in place of the guidelines -- with inconclusive results.

Some of the justices were skeptical of the government's suggestions that overturning the guidelines would cause near-chaos in the federal criminal justice system. Ninety-seven percent of federal cases are resolved through plea bargains, not jury trials, Justice John Paul Stevens noted, adding that, of the 3 percent of cases that do go to trial, few end with sentences that would, in practice, violate defendants' rights.

Ginsburg noted she had been advised that, since Blakely, federal prosecutors were simply writing longer indictments, with more facts specifically alleged.

"Is that so intractably difficult?" she asked Clement.

Clement responded that the more complex indictments made it harder for judges to properly instruct juries.

But Clement's insistence on the "difficult remedial issues" the court would face if it scrapped the federal guidelines did make an impact on some members of the court. These justices entertained the possibility of making the guidelines advisory, or preserving those parts of them that do not involve judicial fact-finding.

"What about all the guideline factors that are not easily presented to a jury?" Ginsburg suggested to Christopher Kelly, a lawyer who was arguing against the guidelines. She added later: "Wouldn't the defendant much rather not have all this negative material tried to the jury?

Kelly replied that judges could be counted on to prevent defendants from being harmed.

But Justice Sandra Day O'Connor, who had dissented vigorously in Blakely, predicting that it would have "disastrous" consequences, seemed disinclined to let her colleagues escape the full implications of their decision in that case.

When Clement observed that he saw "no obstacle to making [the guidelines] voluntary," O'Connor, who had remained silent for most of the argument, broke in. "That seems so contrary to what Congress intended," she said. "It's a real stretch," she added.

The two cases argued yesterday are U.S. v. Booker, No. 04-104, and U.S. v. Fanfan, No. 04-105.

The court would normally have until July to issue a decision, but given the judicial system's demand for a clarification of Blakely, the court faces strong expectations to issue a ruling much sooner.