A federal judge on Thursday refused to postpone the first military trial set for next week at the Guantánamo Bay detention center, rebuffing a last-minute plea from lawyers for Salim Hamdan, an accused member of Al Qaeda and Osama bin Laden's former driver.

Judge James Robertson, of the district court in Washington, ruled that Hamdan's claims that the military commission he faces is unconstitutional can be appealed to a civilian court only after his military trial is completed.

The ruling clears the way for the start of the first trial of a detainee at the prison complex in Cuba, opened in 2002 to hold prisoners captured in the campaign against terrorism. The trials have been delayed for years, in part by courts that found legal fault with the commissions created to try people designated by the government as "unlawful enemy combatants."

It was Judge Robertson who ruled in 2004 that the original procedures set for military commissions by President George W. Bush were inadequate, a finding later upheld by the Supreme Court. In response, Congress in 2006 passed the Military Commissions Act, setting up new procedures for the trials.

On Thursday, after hearing two hours of arguments from lawyers for Hamdan and the government, Judge Robertson said the congressional action was sufficient to permit the trial to begin.

Judge Robertson noted that his ruling applies only to the case of Hamdan and is not binding on the many other Guantánamo cases pending before other judges. He also did not rule on what he said was a central question, the constitutionality of a provision of the Military Commissions Act that permits only limited appeals by Guantánamo detainees to a single court, the United States Court of Appeals for the District of Columbia.

The ruling came after two hours of arguments from Hamdan's lawyers, Neal Katyal and Joseph McMillan, and a deputy assistant attorney general, John O'Quinn.

Hamdan's attorneys argued that to proceed with the military trial now would irreparably injure Hamdan, because the "rulebook" governing such novel trials is uncertain and because testimony based on hearsay and coercive interrogation methods will be allowed.

"At a minimum, Mr. Hamdan deserves his day in court "” this court," Katyal said.

O'Quinn replied that the rulebook for the military trials is laid out in the law passed by Congress, and that any challenge from Hamdan should come only after his trial is over.

Judge Robertson, appointed by President Bill Clinton in 1994, is known not only for his earlier ruling in the Hamdan case but for resigning in late 2005 from the Foreign Intelligence Surveillance Court, which oversees eavesdropping by the National Security Agency.

His resignation was widely viewed as a protest against Bush's decision to bypass the special court after the 2001 terrorist attacks and to permit eavesdropping without warrants against people in the United States suspected of terrorist ties.

At Guantánamo Bay, a military court pressed ahead, as Hamdan's chief military defense lawyer, Lieutenant Commander Brian Mizer, mentioned that the defense team had worked for years to vindicate what it has claimed are Hamdan's fundamental rights.

Court officials have said that they plan to assemble a panel of military officers "” a military style of jury "” in Guantánamo on Saturday. The first proceedings in the trial could be held Monday.

This Wednesday and Thursday the military judge in the case, Captain Keith Allred, issued two rulings that rejected central constitutional arguments of the defense, which had hoped that the Supreme Court's June ruling in the case of Boumediene v. Bush had conferred broad constitutional rights on the detainees in Guantánamo.

In his ruling on Wednesday, Judge Allred seemed to acknowledge that the Supreme Court's decision did give detainees a right to raise constitutional questions in the military courts here, which would be a major departure from the position of the military prosecutors. But, Judge Allred quickly then rejected the particular constitutional claim the lawyers had advanced in one of their legal challenges.

In the ruling, Judge Allred rejected the defense claim that the charges against Hamdan were improper, claiming that they had been enacted retroactively at a time when Hamdan was already in custody at Guantánamo. The defense claimed that was a violation of the provision of the Constitution saying Congress cannot enact such ex post facto laws.

But Judge Allred found that the illegal conduct alleged in charges against Hamdan, conspiracy and providing material support to terrorism, were long barred by the international law of war. He noted that in its 2006 Military Commissions Act, Congress explicitly said that the law enacted to prosecute Guantánamo detainees "does not establish new crimes."

Defense lawyers said they were encouraged because Judge Allred's decision appeared to acknowledge for the first time that lawyers for a detainee could raise such constitutional questions. But any encouragement for the defense was quickly dashed.

A decision in Hamdan's favor would have required the dismissal of the war crimes charges against him. Instead Judge already said he saw no violation of the constitution in the charges. "The commission," he wrote, "is inclined to defer to Congress's determination" that the charges were not new offenses, but were simply defining illegal conduct.

While the court was proceeding Thursday, court clerks released a second ruling that rejected a central defense claim. Hamdan's lawyers asserted that the detainee's constitutional right to equal protection of the laws was violated because only aliens "” not American citizens "“ can be prosecuted for war crimes in Guantánamo.

Judge Allred also quickly rejected that claim in a six-page decision. He noted that the Supreme Court's ruling in June giving the detainees rights to file habeas corpus suits was limited and that the court suggested a practical analysis of other constitutional questions at Guantánamo.

He concluded that military commission trials afford detainees many legal protection, including legal representation, the right to be found guilty only by evidence beyond a reasonable doubt and the right to a public trial.

"In light of this substantial array of privileges and protections accorded to Mr. Hamdan," he wrote, "the commission does not find that the Equal Protection Clause needs to apply at Guantánamo Bay to prevent injustice."

Scott Shane contributed from Washington and William Glaberson from Guantánamo Bay.