WASHINGTON - A federal judge on Monday delayed accused Sept. 11 conspirator Zacarias Moussaoui's trial by six months until June after he complained about the overwhelming amount of evidence to go through and the recent disruption of his preparation caused by a government mistake.

In the second delay of the trial, U.S. District Judge Leonie Brinkema said failure to grant a postponement could cause a miscarriage of justice. She said a delay would give the parties sufficient opportunity to adequately prepare.

Moussaoui, who is acting as his own lawyer, complained about the disruption of his preparation for trial when the U.S. Marshals Service had to go into his jail cell in late August and in early September to retrieve classified documents the government turned over to him by mistake.

The judge also ruled that Moussaoui must be moved to a larger cell, saying that keeping him in his existing small and windowless cell would be both "inhumane" and "an unreasonable barrier to his ability to work with the materials produced to him."

'A BIGGER CAVE'

She said his motion entitled "to Get a Bigger Cave to Prepare the WTC (World Top Circus)" was granted in light of the lengthy delay of the trial date and that he must be moved "as soon as practicable."

The 34-year-old Frenchman has been charged with six counts of conspiracy in the Sept. 11 attacks. Four of the charges carry the death penalty. Moussaoui is the only person charged in the United States in the Sept. 11 attacks.

He has denied being a part of the hijackings, but admitted to being a member of al Qaeda. The United States blames Osama bin Laden and his al Qaeda network for the attacks that killed about 3,000 people.

Moussaoui's standby lawyers and federal prosecutors supported his request for a six-month delay in the trial.

The judge said the trial would start on June 30, with jury selection to begin on May 27.

Some U.S. officials have said Moussaoui, who was being held on immigration charges on Sept. 11, was meant to be the 20th hijacker. The plane that crashed in Pennsylvania had only four hijackers while the other three hijacked planes that hit the World Trade Center and the Pentagon each had five.

The latest delay meant that Moussaoui will go to trial more than 1-1/2 years after his indictment in a case that has caused numerous headaches for the government. The court where the case is pending has been dubbed the "rocket docket," normally known for its quick trials.

The last time she delayed the Moussaoui trial in mid-August, Brinkema set a Jan. 6 trial date, with questioning of potential jurors beginning on Dec. 9.

According to court documents released last week, the U.S. government gave 48 classified documents to Moussaoui by mistake over the past few months as part of the huge amount of evidence turned over to him by the prosecutors.

The classified documents -- FBI summaries of interviews -- then had to be retrieved during several days of searches of Moussaoui's jail cell in Alexandria, Virginia, where he is being held in solitary confinement awaiting trial.