A Bush administration campaign to win blanket congressional approval for the military commission system set up to try Al Qaeda members for war crimes is encountering stiff resistance on Capitol Hill.

Administration officials testifying before Congress for the first time since the Supreme Court struck down President Bush’s military commission order urged lawmakers to give their imprimatur to the same plan the court rejected as at odds with existing law and America’s obligations under the Geneva Conventions.

“The most expeditious way to do it would be to essentially ratify the process that’s already in place for military commissions,” the principal deputy general counsel at the Department of Defense, Daniel Dell’Orto, told members of the Senate Judiciary Committee.

The Supreme Court’s June 29 ruling in Hamdan v. Rumsfeld suggested adopting the rules for courts-martial under the Uniform Code of Military Justice, although the court did not foreclose other possibilities.

“I guess the lesson learned from this court case is that collaboration is always better than unilateral action,” Senator Graham, a Republican of South Carolina, said.

However, Mr. Dell’Orto and the acting head of the Justice Department’s Office of Legal Counsel, Steven Bradbury, told the committee that the military code was not a feasible basis for war-crimes tribunals.

“The court-martial procedures are wholly inappropriate for the current circumstances,” Mr. Bradbury said. “We don’t think it’s appropriate to start with the UCMJ and talk about specific procedures that should be stripped out.”

In several tense exchanges, Mr. Graham told the administration officials that any military commissions had to be based primarily on the court-martial procedures. “If you fight that approach, it’s going to be a long hot summer,” the senator said.”I think you would be well served to forget about Military Commission Order No. 1,” he said, referring to rules the Pentagon issued in 2002 setting out procedures for the tribunals.

Mr. Graham’s blunt criticism of the administration’s approach was striking because he is a former military lawyer and led an effort last year to limit the rights of detainees to file habeas corpus petitions in civilian courts. About 450 war-on-terror prisoners are being kept at Guantanamo Bay, while hundreds more are in Afghanistan, Iraq, and elsewhere.

The chairman of the committee, Senator Specter, also clashed with the administration officials. When Mr. Specter, a Republican of Pennsylvania, asked for advice on legislation establishing a congressionally-authorized procedure for determining which detainees should be kept and which should be released, the administration lawyers demurred.

“That is a question we believe should be left up to the Department of Defense,” Mr. Bradbury said.

“I doubt very much that Congress is going to be disposed to leave these issues to the Department of Defense,” Mr. Specter said heatedly. “The Congress is going to establish the policy. That’s our job. … We’re not going to leave it to the Department of Defense or give the Department of Defense a blank check.”

While the administration pressed for a quick legislative response to the court’s decision, the top Democrat on the committee, Senator Leahy of Vermont, said the delays and legal setbacks could have been avoided if the executive branch had supported bipartisan legislation put forward on the detainee issue in 2002.

“Basically, you told us to take off,” Mr. Leahy said. “Four-and-a-half years later, nobody’s been brought to justice.”

“This president and this administration acts as if they are the whole government,” Senator Schumer, a Democrat of New York, complained. “Time and time again, the president acts like a bull in a China shop and sets back the war on terror.”

Mr. Bradbury acknowledged being “quite surprised and disappointed” by the Supreme Court’s ruling, but said the military commission order was not designed to expand presidential power.

“It was not crafted to push the envelope,” Mr. Bradbury said. “The procedures were crafted consistent with historical practice.”

On Friday, the Defense Department formally notified its personnel of the Supreme Court’s decision, including a holding that all detainees are protected by Geneva Convention provisions barring “humiliating and degrading treatment.” The Pentagon directive was first reported by the Financial Times.

Mr. Bradbury said the phrase was “susceptible of uncertain and unpredictable application.”

Mr. Graham said he would press for legislation to “rein in” the impact of the court’s ruling on that point.

The administration lawyers said according Al Qaeda operatives the rights applicable to American soldiers and sailors accused of crimes would make it all but impossible to proceed with war crimes trials. The attorneys said the proceedings could not comply with rules about hearsay, evidence handling, and mandatory warnings against self-incrimination. “It is simply not feasible in time of war to gather evidence that meets strict criminal procedural requirements,” Mr. Dell’Orto said. “It would be ludicrous in my estimation to accord those sorts of rights at that that level to that degree to the sorts of people we have here.”

Senator Sessions, a Republican of Alabama, said giving so-called Miranda rights to Al Qaeda prisoners made little sense. “We don’t need to be providing that kind of privileges to people captured on the battlefield,” he said.

Senator Biden, a Democrat of Delaware, said the Guantanamo prison camp and bold administration claims of authority to use practices some consider torture were undermining American national security.

“You may get one detainee through actions that the rest of the world views as totally illegitimate and inconsistent with who we are — although arguably constitutional, and as a consequence of that produce four more suicide bombers,” he said. “I’m telling you things ain’t good in Happy Valley.”

“The world we live in is a dangerous place. It’s not Happy Valley,” Mr. Bradbury replied.

Senator Durbin, a Democrat of Illinois,said the Geneva Convention limits would have no impact on one of the most successful interrogation techniques at Guantanamo, offering McDonald’s food to prisoners.

“They hand them Chicken McNuggets. They love it, and they start to talk,” Mr. Durbin said.