US judge rejects Rumsfeld interview.
Judge Colonel James Pohl also suggested he would compel top military intelligence commanders to testify unless prosecutors move forward with criminal charges against them by September 17.
So far, the commanders have refused to testify on the grounds they could incriminate themselves and later face charges.
The request to interview Rumsfeld, along with his deputy Stephen Cambone, was made by a lawyer for defendant Specialist Javal Davis at a pretrial hearing in Mannheim, Germany.
While Pohl rejected it, he said it could be brought back if the defence can fill in some of the gaps.
'There's got to be some links in that chain,' Pohl said.
Davis and the five other military police accused of abusing prisoners at the Baghdad prison insist they were following orders from military intelligence officers and civilian contractors.
Davis's civilian attorney, Paul Bergrin, asked the court to grant immunity from prosecution to Colonel Thomas Pappas, the military intelligence commander at Abu Ghraib, and several other officers who may have known of the abuse but have refused to talk to investigators, citing their right to avoid self-incrimination.
A grant of immunity could remove that obstacle, but prosecutor Major Michael Holly argued that the officers themselves could face charges after the military completes a report into the role of military intelligence at detention facilities, which is expected to be presented to the US Congress next month.
The additional evidence could broaden the case beyond the six low-ranking Army reservists and raise the possibility that intelligence officers and others within the military encouraged abuse to gain information about Iraqi insurgents battling US troops.
The judge gave the prosecution until September 17 to convince him that they should not be compelled to testify.
Pohl made it clear, however, that if the government does not intend to file major charges against the officers by then, he would probably grant them immunity to testify.
'This would appear to be critical information to the defendants ... that this was condoned by the higher-ups,' Pohl told the prosecutors.
Later, Holly said he expects two US military intelligence soldiers who worked at Abu Ghraib, Specialist Armin Cruz and Specialist Roman Krol, to be charged soon. Those would be the first charges against members of military intelligence, though the prosecutor gave no details.
Signs of a plea bargain emerged for another defendant, Staff Sgt Ivan L 'Chip' Frederick. He was the senior enlisted officer at Abu Ghraib between October and December, when the mistreatment allegedly occurred.
Military prosecutors agreed to drop some of their charges after Frederick agreed to plead guilty to the rest at an October 20 sentencing hearing in Baghdad, his lawyer, Gary Myers, said.
However, the judge rejected a defence request to move Frederick's proceedings out of Iraq because witnesses would be afraid to travel there.
The scandal erupted last spring when photos became public, causing worldwide outrage about the physical abuse and sexual humiliation of inmates.